Theme?
It would be good if you were to specify a theme...but i will give it a shot:
Illusionist
A light melee hero that confuses and dazzles enemies.
Examples of abilities
Decoy - creates a decoy that has the taunt ability, and that also has the same model as the hero. This would be simple - edit serpent ward to have taunt and no attack and change model to whatever.
Mirror beam - summons a powerful beam of magic that damages the illusionist and his target. Base off chain lightning, remove bounce, change lightning effects to drain mana.
Trigger:
Unit begins casting an ability
Ability = mirror image
Set (life of casting unit) equal to the (life of casting unit) - 100*
*change as appropriate
Confusion - causes a targeted enemy to wander around aimlessly for a set amount of time. You could use triggers to give the target 'wander' ability.