Describing how a creature is different from all creatures is a little more important than listing a large list of numbers, so im going to skip all of that.
This creature is basically a monkey-like creature, that lives in the trees of loreroot. Hopefully this isnt too hard to add in MD, but basically, the trickster just does a lot of random things, either to your own army, or theirs.
When you choose targets for the creature, you can either choose "Random-friendly" or "Random-enemy", or just have it be completely random and happen to either army. This is because the only attack that it does is called "Random effect", which is different from random damage. Basically, it will choose a random attack style "steal life, heal, protect, random damage, etc" and apply it to whichever target it decides to apply it to.
Two examples: It could target an enemy creature and cast protect or steal life on it, and steal life would give one of your own creatures the stolen life. He could also target one of your own creatures with random damage or rejuvenate.
Each time it upgrades, the amount random effects that it can do increases. At level one it can only do random dmg on a random crit, while maxed level itll be able to do all/most abilities that currently exist.
It could have special influences that can affect either yours, or theirs. An example would be +5% attack, or -5% defense, and the effect would apply to one side decided at beginning of battle. If special influences cant work this way, it could just give your army a positive and negative effect all the time, example would be both of the 2 previous effects i mentioned.
The biggest thing that makes this creature unique compared to others is that its a gambling creature. An entire army of them could wipe out the strongest army, or they might all just kill themselves. I'm not sure if gambling is a good idea for fights, but if it is, this creature would be a great start.