The Omniknight is being played in several different ways. You can see him as an ugly chaser with a high MS and a slow (S&Y, Skadi), you can see him stacked with STR items (Heart, Satanic) and as a supporter (Guinsoo, Refresher). The way you are playing him depends on your line-up and match-up, and of course the level of the game.

Basically what I think is that Omniknight is a support hero, that can become a hybrid in many ways. Give him some mana regeneration and then do whatever you want to do and needs to be done to him. If your team lacks a tank, then buy a Heart. If your team fails horribly at carrying and you have the possibility of buying a Radiance, then do so for Christ's sake.

I will go through all of his skills one-by-one analysing them and giving guidelines on how to use them. As it's a Strategy Hero Guide, I will be concentrating more on the strategical aspects than on the unimportant filler sentences allowing this guide to be short, yet helpful and filled with important information.

Purification
Mechanics: the damage is mixed, therefore both armor and spell resistance reduces the damage dealt by Purification. As the game progresses it becomes less and less useful against heroes. Strategics: the way you have to use this spell is waiting for at least until your or an ally's HP drops to a level that if you healed, the target won't have full health pool. The only occiasion when you should be healing someone to full health is when you are harassing an enemy and especially if you can score a frag with Purification. If you need to speedfarm, then you can use this skill for killing the ranged creeps instantly and damaging the melee ones heavily. But otherwise you should not be using it for farming, last hits will be enough if you can learn how to time it well.

Repel
Mechanics: if you cast it on a hero, it will remove most of the casted buffs, doesn't matter if they are negative or positive ones. Most of the target spells won't work on the repeled unit and spell damage are fully negated.
Strategics: while you are laning this spell might be useful in saving one of your allies. Cast it before a stun would land in, or remove some negative buffs. Also if you or your ally plan to rush in, then being able to run in without getting interrupted by a spell is very important. Later it will be used on heroes that are channeling their spells or on the carries. I think in serious games Omni should be picked only if his repel will be in need of at least on one of the heroes.

Degen Aura
Mechanics: the AoE of the slow is 300.
Strategics: this is both an offensive and defensive ability. When retreating it's especially useful agaisnt melee heroes, or when you want to block enemy heroes reaching your allies, Degen Aura is your friend. If you are an agressively playing player and can be agressive in the game, then Degen Aura will help out so well in chasing it will be near to impossible to flee alive from you. Using animation canceling is very important or else you might be slowed down so that you can't follow your target to "channel" (not real channel) the slow aura.

Guardian Angel
Mechanics: gives 98% physical damage reduction and a high additional HP regeneration. The AoE is 1000 on levels. Repel removes Guardian Angel from target.
Strategics: in early game it might save your ass sometimes. Later it will be used in team fights when you jump on your enemies. Don't waste this spell, wait patiently for the perfect time.

The Skillbuild

Basically, there is just one way to efficiently build an Omniknight.

Level 01 - Purification
Level 02 - Degen Aura/Repel
Level 03 - Purification
Level 04 - Degen Aura/Repel
Level 05 - Purification
Level 06 - Guardian Angel
Level 07 - Purification
Level 08 - Degen Aura
Level 09 - Repel/Degen Aura
Level 10 - Repel/Degen Aura
Level 11 - Guardian Angel
Level 12 - Degen Aura
Level 13 - Repel
Level 14 - Repel
Level 15 - Attribute Bonuses
Level 16 - Guardian Angel
17 to 25 - Attribute Bonuses

The justification of the rather easy. Purification is maxed first for obvious reason - it's a heal and your only damaging spell.

Then the confusion begins. Degen Aura or Repel? The answer differs from game to game, respectively from lane to lane. If you're laning against nukers/combo heroes or heroes with damage over time spells, get one level of Repel early. As an example, if you're laning against like Sven and Leshrac, get repel so you can Repel your ally (or yourself) after Storm Bolt hits so Leshrac won't be able to chain (doesn't work all the times, especially when you're the target and they don't leave a gap between the stuns).
Another situation would be when laning agianst Viper, Repel prevents orbwalking and nullifies the damage and the slow of Viper Strike when cast after it. Two levels of Repel at level 2/4 should only be taken when you're leveling against Venomancer (to block 10 from the 12 seconds of Poison Nova) and maybe against Doom Bringer, though it's only useful when he's casting Doom on your ally, else you're silenced and can't cast that spell anyway.

From that point on it's more or less at your disposal how you're chosing the skillbuild. I recommend that you're having 2 levels of Repel when reaching level 11, and that you finish Degen Aura by level 12.

Guardian Angel should be taken whenever available, it may always save your or your allies' asses when ganked or when diving a tower.

The Itembuilds

I decided to make only one core item build, which is quite flexible. I will rather discuss some possible alternates in a different section.

Basically you need some form of mana regeneration. You won't be spamming your spells, but when there's a big battle, you will spend a lot of mana in a considerably short time. So burst regeneration is the best for you, which can be found in Bottle or Arcane Ring. Wether to choose Bottle or Ring depends on the game rules. In most tournaments only one Arcane Ring is allowed per team, and if there's a hero that needs Arcane more than you, then get Bottle.

Observer/Sentry Wards are to be gotten by you, because even if you don't have much items, you can still be a helpful hero in your team. TP scrolls are to be gotten till you buy Boots of Travel. You don't need Power Treads, because you will be supporting not by the physical damage you deal. Movementspeed is much more needed for you than Attackspeed. Also, being able to teleport helps a lot, too.

Arcane Ring - undoubtly the best mana item for the Omniknight. It boosts your manapool by a lot and the burst mana regeneration will make sure that you can cast your spells all the time. I think this item was made especially for heroes with low starting INT, mainly the STR heroes.

Bottle - if you want to rush an expensive item or you are playing in a tournament/league where only one Arcane Ring is allowed per team and one of your allies is already making it (Zeus, Ogre Magi, Earthshaker etc) then Bottle is to be gotten on this hero. The fact that you regenerate health along with mana will allow you to use your Purification on your allies instead of you.

Bracers - wraiths are obviously not needed on this hero. Null Talismans look appealing, but the fact is that a Bottle and especially an Arcane Ring already fixes your mana issues. However you need survivalability and the ability to farm neutrals faster and Bracers is just perfect for these purposes. Of course if you have no problems surviving, just don't upgrade the circlets, they will be enough (especially if you go for Necronomicon).

Necronomicon - a really great item on this hero. He was meant to hold this book in his hands. The MS aura that one of the demons give will allow you to chase more efficiently, the mana burn gives you a high boost on damage as you will not be attacking too frequently. The attribute bonuses are both needed, a little STR and a nice amount of INT. Especially if noone else is heading for this item you are to be getting it as a Necronomicon 3 will allow you to destroy wards, detect mines and invisible heroes.

Radiance - we could as well call it the Carry Item. The immolation allows you to farm neutrals fast and speed-farm in lanes, so it becomes harder to catch you. In case you can farm up the 3800 golds early on, this will be a great addition to your inventory. Suggested mainly for pubs and fun IH games.

Some Further Item-Discussion

In this section I would like to mention some of the better and some of the not so good items for the Omniknight. I will give justifications when and why to use certain items, and why others fail horribly.

Heart of Tarrasque - this is a great item for Purist Thunderwrath. Sometimes you need to become the tank of your team and as you need to be near to your opponents to make use of Degen Aura or need to be around your allies to use Guardian Angel there can be no question why. Also if there are no better heroes to cast Repel on, and it's you who get the benefits of magic immunity, then you need to be able to tank physical damage.

Eye of Skadi - some players like to buy this item, while the most players bash it instead. I say that it's a viable choice for Purist, as the slow, the mana and helath pool, everything is good for him. The problem is that it costs 7050 golds and it is really hard to farm it early enough. Rush it only in fun pub games or get it after Radiance. I would not recommend it in any other cases.

Assault Cuirass - as you have a relatively slow attack speed and as you are a melee hero, this item can be of a good use for you. With Repel on and an AC in your inventory you are basically unkillable. When you are low on health, then you just use Guradian Angel and there's no problem at all. After the core builds are complished and either there are no magical threats or you are a better repel-user than your allies, buy this item.

Hood of Defiance - when you have allies that MUST be repeled all the time, but you die to nukes in team fights all the time, then Hood is a really useful item. It's easy to farm it up and let's you tank all the damage done in team fights.

Sange & Yasha - the item that many hate and many love. Actually it's not a bad item on this hero, it's easy to farm up and you benefit from everything this item gives to you. The only problem is, that you can always find better alternatives. I myself rarely get it on Omni.

Guinsoo's Scythe of Wyse - this used to be a very much liked item on the Omniknight. It was gotten on this hero because he needed some form of mana regeneration and manapool. The Cyclone and then the Hex abilities are really useful. The only problem is, that both Arcane Ring and Bottle are thousand times better to fix your mana problems and a Necronomicon suits this hero much more (giving STR, MS/AS auras, manaburn). I haven't bought this item for Purist for more than a year.

Refresher Orb - a great item especially if you went for the Basic Build with Arcane Ring. Double Guardian Angel and double Repel is an amazingly powerful combination and can easily determine the outcome of a fight in lategame. The only problem is that you can rarely get to buying this item.

Mekansm - you can heal the hero that is repeled. Great auras as well. Good thing. The bad part is, you already have a low manapool and heroes with high starting INT should be getting this item instead of you.

Omniknight Techniques

Puri-Harass:
There are two ways of harassing with Purification. One possibility is that you run up to your enemy, and then heal yourself, so the enemy takes damage. This technique isn't that easy to execute and could horribly backfire when you're not paying attention. The hardest part about this technique is that you have to place yourself in a way so your enemy is still within the AoE of Purification when you're casting the spell, and doesn't run out of it when you're standing still and raising your hammer towards the sky to recieve the heal. The risk with this technique is that the enemy can simply disable you when you're behind the creepline, and then you're in trouble.
The second possibility is that you heal a creep which is attacked by an enemy. The upside is that the enemy can't counter this, besides standing out of the AoE which would mean no farming for a melee hero, but the downside is that you heal a creep and not yourself. An alternative is when you heal an ally of yours that is standing near to an opponent.

Puri-Farm:
Again, two ways to farm with Purification. One possibility is that you run into the creeps and heal yourself. Notice that Purification instantly kills randed creeps at full health within the first 50 minutes, after that the Necromancers/Druids of the Talon have more than 360 hp, so this won't work again. You make best use of this when there are some melee creeps below 360 hp, and you perform this by placing yourself approximately in the middle between the ranged unit and the melee units, then heal yourself. Like this, you should be able to damage/kill both, rangers and melee units. Alternatively, you can simply wait until all of your creeps are dead, then run next to the ranged unit (with the melee units tailing you as you're the only enemy left), then heal yourself. Dangerous when there's still an enemy around.
The second possibility is healing a creep when some enemy creeps are below 360 hp. You can as well run straight towards the enemy creeps, while your own creeps are far behind, pulling them around you and then heal yourself after hitting some of the creeps. Especially easy to farm this way if you have a Radiance.

Remedy-Repel:
All you need to do to be able to perform this technique is to pay attention. Repel the unit that is either going to be the target of magic spells (as an example, Sven just stunned your ally and you see a Lina popping out of the forest - Repel your ally, and Lina's spells will go to waste, as they're both do not require to click on the unit, so there will be no "Cannot target" error message) or allies that are suffering from Damage over Time spells, such as Shadow Strike, Posion Nova, Viper Strike, Doom etc. Notice that Repel does not remove these spells, but blocks the damage as long as the spell lasts. If your enemy has ordered to cast a targeting spell on a unit, and you repel that unit in between, the spell is still going to be cast but won't deal any damage.

Repel-Channel:
Repel-Channel, or "How to save my ally 3800 golds from buying a Black King Bar" means nothing but casting Repel on an ally who has a channeling spell, such as Crystal Maiden (Freezing Field), Enigma (Black Hole), Bane Elemental (Fiend's Grip) etc. Talk with your ally, tell him that he should ask for a Repel before jumping in, so the chance of being disabled during the channel is zero.

Carry-Repel:
This is very simple, before or right at the start of a Teamfight, repel your main damage-hero so he doesn't have to be afraid of being disabled. Repel heroes that rely on their physical damage output, such as Shadow Fiend, Viper, Clinkz, Silencer, Troll Warlord etc. Being able to engage for up to 20 seconds without being thrown back by a disable and nuked to death really means something, believe me.

Degen-Block:
This is a technique you should use when you and at least one ally are chasing an enemy hero. Try to get in front of the enemy, so he is caught in your Degen aura, losing 28% of his current movespeed, and then try to block him as you'd block the first creeps that spawn in the game. With your enemy being caught in the Degen Aura, you can react much faster to his movements, always blocking the path in front of him.

Degen-Walk:
This is the alternative to the Degen-Block. Walk next to your enemy, so he's caught in the Degen Aura, and walk all the way by his side, so your allies can catch up. Very important here is that you don't attack him (as in right-click on the hero), but always right-click on the ground in front of him, so you're walking the same way and he can't get rid of the Degen aura. Especially important against heroes with much higher MS than what you have. Really annoying for the enemies If you want to flee from melee heroes or summons, then Degen Aura will be your best friend.

Angel-Save:
So, there's your ally, in the river, and there are those two enemies, pounding on him like there is no tomorrow. What do you do? You try to get within 1000 units to your ally, and then hit "G" to activate Guardian Angel. Gaining 1000 armor (also known as "almost complete physical invulnerability") and a regeneration of 25 hp/sec, your ally doesn't have to be afraid of dying until the GA-buff wears off. Meanwhile you run to your ally, use Purification and Repel as soon as GA is gone (not before, else you'll remove GA!) and run with him to slow down the enemies if they try to catch up again.
You should NOT use this technique if your ally is already very low on health (as in, about 100 hp) and one of the enemies engaging him is a spellcaster. Guardian Angel does not block incoming spells at all, so it would be a waste of your ultimate casting Guardian Angel, and then Lion hexing/fingering your ally to death.

Angel-Jump:
Your signature move in teambattles. Basically this means that you're casting Guardian Angel during a teambattle, to turn the tides because all your allied heroes (and all your creeps) are invulnerable to physical attacks. However, there are to two things you should keep in mind.
The first one is the timing of this spell. You shouldn't cast it right in the beginning, as the enemy would simply back off and wait those 5/7/9 seconds, then come again. Also, you shouldn't cast it when one or two of your allies are already dead, while your enemy hasn't lost any, because like this it will just look like a runaway move. Cast it before one of your allies is dead, but when the battle has already fully developed, so your enemies can't just back off without suffering heavy defeat/losses. The other thing is that you shouldn't cast Guardian Angel and then Repel someone right afterwards. Repel before, then use GA, else Repel will override GA for whoever just gained spell immunity.

Omniknight Strategies

Laning - Purist is a rather weak soloer, although against melee heroes he does really fine as he can adapt to any circumstances. However in organized games you will see him paired up with a ranged hero, who has a nuke, a stun or a slow at least, which will allow you to take the lane control. If you face troubles, you can always use Puri-Heal or Remedy-Repel. Puri-Harass should be used when you assured lane-control. Otherwise spare your mana for the worse times.

Soloing - as I said, Omni isn't that good at soloing unless put against a melee hero. Ranged heroes are probably going to out-micro you and won't allow you to get any last hits/creep denies. Try to play conservatively against them and go in only for the last hits or when he is over-confident and makes a big mistake, then use the Puri-Harass technique. Against melee heroes you are going to max Degen Aura before putting points on Repel, as it allows you to harass the hell out of them and maybe score a kill. Heroes like Nerubian Assassin will be really harmful for you. Spam all your spells before he does much harm to you. Against Ogre Magi you might want to get Repel, because a hero might come over to help him and that will hurt you. Against many dual and especially tri-lanes, get 2 points on Repel, too. This all depends on wether you'll be nuked/disabled or not. You have to be observant.

Getting Ganked - when you see someone trying to gank you, or a spell is heading towards you, then immediately put Repel on yourself. After that run back to your tower and if needed, then heal. If you fail to cast Repel in time, cast Purification first, then Repel and then Guardian Angel. If you managed to cast Repel in time, but their physical damage is so hurting you, then cast Guardian Angel this case as well. If you don't have Repel, then try to juke you and/or ask for you ally's help. Try to calculate wether a guardian Angle will be in need or not and cast it in case it is needed. It is something I cannot teach in words, you will learn it only the hard way: game experience.

Ganking - this depends on wether you go to another lane, someone else came to your lane, you have Repel or you have Degen Aura or both. If you have Repel, then put it on the ally that can deal out the most damage or on someone that can chain-disable. If you are on a high level, then cast it on yourself and use the Degen-Block technique, which is uncounterable. It all depends on your allies and the ganked hero(es). If your allies come to gank your lane enemies, then start running towards your opponents soem seconds before your allies would be revealed. If someone is heavily damaged AND is near enough an enemy, then cast Purification on the target ally (or yourself). If you go gank an enemy in your ally's lane, then most of the time you will want to go from behind, to block the target's way with Degen Block and then using Puri-Harass (and probably stealing the kill ).

Farming - while laning, you should never use Purification to gain gold. Only exceptions are when you would use the Puri-Harass technique or either you or your ally is on lower health. When the lanes mix up and everyone is ganking around, sometimes pushing as well, you will already have a Bottle or an Arcane Ring. At that time of the game you may use the Puri-Farm technique. Neutraling is also viable from mid game. Just hit all of them as much as to getting them instantly killed by a single Purifitcation. This way you won't lose HP and you will clear a whole creep spawn.

Pushing - this again depends a lot on game situation. If your allies are pushing a different lane AND all the enemies are defending there, then you need to push your lane as fast as possible. For that you need to rush towerd the next creep wave leaving your own creeps behind. Use the Puri-Farm technique's creep pulling version. If you went for the necro build, then cast the demons when the two opposing waves collide. This will ensure your creeps have a higher DPS and they can run faster, fastening the push as well. If you push with your allies, use Puri-Farm only if you do need the heal. Otherwise stay aware of the situation and cast Repel on your carry hero if you get ganked. Use Guardian Angel as well, turning the tides of the battle.

5v5 Battles (defensive) - when trying to defend an outer tower, you will need to stay behind the tower and waiting for the best opportunity to initiate. If you have no problem keeping your carry hero or ulti-channeler repeled, then don't hesitate using it every time it cools down. Your role is waiting patiently, while your AoE-spammers (Leshrac, THD, Zeus, etc) are clearing up the upcoming creep waves all the time. Once the enemies initiate use Guardian Angel immediately and if you have necrobook, then cast the demons (try to do that before using GA, though). However if your opponents screw up and hesitate for too long, you might try to initiate. Wait for the best opportunity: you just used repel on an ally AND one of the opponents don't retreat in time or run in without the others. If that happens, then summon the demons immediately, burn the mana of the poor enemy. If his allies run in, then execute the Angel-Jump technique.

5v5 Battles (offensive) - when your team is trying to gank all the heroes of the enemies then use either the Carry-Repel or the Repel-Channel technique. After that, do the Angel-Jump and you are probably going to heavily win that battle. That was the easier version. However when you are pushing and especially if you try to push inside the base - when you don't have vision over the enemies - you will have to be very very careful. If there are heroes like Silencer (Global Silence), Warlock (Infernal), Pugna (Nether Ward), wait until they waste their spells. You need them to initiate and to fail. It's not that risky if your tank goes close with Repel on him, because you'll be able to heal him up later or go jump in with Angel-Jump. It all depends on game situation, but as I said, try to wait until your opponents do a fatal mistake, which will allow you to smash them into pieces.
Source : www.garena.com