Chaos is the replacement for Nightmare difficulty however with different mechanics and enemies. Players will need to utilize the new Shards system, Ascension, and strategize in hopes of beating the new Chaos difficulty.
Each Chaos tier introduces a new enemy.
In C1 you will first encounter Vanguards - shield goblins. They have a very high resistance to direct front damage, the best strategy against them is to use traps, auras, magic towers (like Ramster or Flamethrower) or build direct damage towers behind them.
Cyborks are an anti-trap/aura/node enemy introduced in Chaos2. If you’re attempting to take down Cyborks with these defences, you’re going to have a hard time.
Shield Geodes are introduced in this tier. They are crystals that emit an energy shield that reflects projectiles. Strategies against them are similar to C1 Vanguards, but because they have a shield all around them, placing towers from behind won't work, forcing a different approach.
This Chaos is centered around the Berserker Orcs (commonly called "Lady Orcs"). Berserkers are all about being fast and dealing high damage upon reaching defenses, so using crowd control effects like stuns and knockups to slow them down are your main counter for this threat. Cyborks counter most of those kinds of effects, so you won't see Cyborks in this Chaos tier anymore, but there will be Shield Geodes and Vanguards present.
Chaos V is all about Dark Assassins. As opposed to other enemies, Dark Assassins instead focus player heroes. They sneak up on players, at which point a purple fog gathers around you - they will then teleport to you and deal a great amount of damage and afflict you with silence, preventing you from using all your abilities and basic attacks, all you can do is run around and activate pet abilities. The best way to get Dark Assassins off your back is to run to your defences/allies so they can kill it, activate immunity pet skill or stun them. The most popular method is to utilise Cannons with Stun Fire or Heavy Cannonball shards in par with Sharpened Spikes shard on blockades. Assassins attack in a cone, so you can easily fail the map by running around defences or the Core with Assassins on your back. In this tier you will also encounter Cyborks, Berserker Orcs and sometimes a single Shield Geode per wave (usually can spawn in wave 3 and later ones), it's crucial to check where it will spawn and kill it as fast as possible on this difficulty level.
Hex Throwers are the main threat of this tier. They are ranged enemies with the longest range in game and throw javelins that can curse your defences. Don't forget that you have to deal with all special enemies you met on previous Chaos tiers (except Cyborks). Keep in mind that Dark Assassins appear at wave 3, 4 and 5. At wave 5 you have a special surprise, a Hex Thrower in the form of a boss will appear. The best way to defend against the cursed javelins of a Hex Thrower is to use the Reflect Beams of the Series EV2 hero.
A new flying threat is introduced in this tier under the name Kobolts. They will aggro your defences and suicide with an explosion on them if they are close to their paths. In the event your towers survive the impact they'll be stunned for the next 20-30 seconds. All previous special enemies make their appearance as well in this tier. At wave 5 there is usually a special surprise, the Zapper, a boss type enemy with the abilities of a Kobolt.