Here comes some ideas for characters
Medusa (the Classic form, human with snakes instead of hair or a snakes body with human upperpart and snakes instead of hair) - Ability : Then attacked in the front she stuns the enemy for X turns (x is to be decided).
Werepeople, (I really liked the idea of the kid becoming a ghost). So I thought about werewolf turning from a human to a werewolf. But why stop with werewolf, why not a werebear, weretiger and so on. Perhaps having a character to be a werething and then randomly decide what kind of werecreature it is and they all have different abilities.
Another kind of character is the different hybrids of animal who is humanized like Catpeople and so on.
A basilisk, the medieval version (the front of the body is like a roaster and the back is like a snake).
More to come later
Werewolves could become anthro wolves instead of normal wolves, in a bit of homage to Aground.
When a werewolf is in its wolf form, it reverses its attack and health (so a 0 or negative attack guy becoming a wolf would result in death)
Dogs can't be mutated, but cats can already be mutated, as are the fennec foxes.