Champion concept: The mirror.

I didn't add the damage because I know nothing about balance, same for the duration of the stuff. I imagine him as a person made of glass (kinda like silver surfer you know, but with glass).

Passive- Reflection: The mirror returns 10 % of the damage received to the attacker.

Q- Disguise: Takes the form of a targeted ally champion for 15 seconds. The mirror keeps his own stats and items, but the enemies see the ally's stats, name, items, buffs etc... If The Mirror attacks or is attacked, the disguise ends and he returns to his original form. After ending the disguise (after 15 second or after being attacked/attacking), The Mirror's attacks deal bonus magic damage for 7 seconds (ap scaling)

W- Gleam: Deals dmg (ap scaling) and blinds all enemies for 2 seconds in an area around The Mirror, making their basic attacks miss the target.

E- Blink: Sends a light beam that deals dmg and marks the enemy (single target skillshot, ap scaling). Marked enemies are revealed and The Mirror can reactivate the ability to teleport to that enemy.

R- Reflected image: Gains ALL stats and abilities of a targeted enemy champion for 10 seconds (keeps the cooldowns and buffs the enemy had when the ability was activated). If that enemy dies before that time ends, the ability will last 10 more seconds.