Marionette

Target creature you don't control becomes a
player with 20 health and unlimited mana.
Exile the top twenty cards of your library. The
exiled cards act as its library.
On its turns, the creature draws a card and
casts it if possible. It then uses each available
activated ability once (targets are determined
randomly), and attacks a random player with
every creature that can attack.
"I'm through with following orders!"