I have a few sets of ideas to give. Here are a select few.
Bone Dragon:
Desc:
Born from the depths of the dark elixir, a Bone Dragon has a venomous breath that can poison Clan Castle troops and enemy towers! Beware! You can not heal him!
Pros:
Instead of fire breath he uses a neurotoxin like poision breath.
Poison damage multiplies on the affected target by 4 times every 5 seconds
Breath affects all buildings and enemy units in it's range. (Poison can only be removed by Healers and healing spells only)
Wider spread radius (can affect multiplie units) than a normal Dragon.
Rage spells increase the poison spread greatly, as well to rate of fire and damage.
Cons:
Uses a lot of Dark Elixir to create.
Direct Poison Breath does less damage than a normal fire breath from an elixer Dragon.
The Bone Dragon can NOT be healed by spells or healers.
The Bone Dragon has the same health as a normal Dragon.
Revive spell:
Desc:
In need of troops in battle? Revive them with a odd alchemy spell! WARNING: Side effects may occur to the revived units once after the effect has vanished.
Pros:
You revive your decayed units!
Revived units have a 5 second rage given to them. Revived units will have a "R" symbol above their heads.
Cons:
Requires Dark Elixir to create.
Units respawn with HALF Hp.
Healers can not heal them, but healing spells can heal revived units.
Overtime, the longer a unit stays alive it begins to lose sanity and will attack any unit in range both yours and theirs.
You have a 100 unit respawn limit. This can be upgradable to 200 units.
Can not be used on heros.
Engineer:
Desc:
Need a helping hand? Call an expert builder to "manufacture" combat robots on the feild! Combat robots copy most of the abilities as normal elixer units!
Pros:
Like a Witch, He can spawn units within his radius by building robots.
He has a primary attack, which is similar to a wizards lighting bolt that can't be upgraded.
Has great health, moves fast, and can jump walls!
Cons:
Uses a lot of normal elixir to create.
Robots are spawned at random (see robots below)
Tends to Avoids walls. (This means that he can't get too close to the base.)
Has a building timer, it takes him a while to build a robot, he is marked with a wrench when building. He can not attack while building.
Robots:
Desc:
Robots are weird little bits an engineer can make. They can copy a normal elixir's power at random. Though, they love electricity, the will melt if the get too close to any source of heat.
Pros:
Ability to copy a normal elixir's type. But is called diffrently.
Robot names rates and damages can be given by supercell:
Punch-bot (Barbarian) uses metal fists to attack.
Lobber (Archer) lobs rocks in a range!
Miner-drone (Goblin) Rushes with a small drill to sap away at resources.
Fire-MOAB (Bomber) Instead of explosives it uses fire to do multiple damage to units around itself! Then it explodes! (does less damage to walls)
BlockHead (Giant) acts like a giant with higher rate of fire.
More robots to come.
Immune to attacks that use electricity: Thunder spells, Wizards level 4 and up, Hidden Teslas. In fact, the get a rage boost if they come in contact with these sources.
Cons:
Instant death if they come in contact with any source of heat.
Can not be healed.
Explodes on death to ALL units in the area. Including your own.
Can only be produced by an Engineer.
That's all I got. But I'll add more later on!


