The puppet

When this card enters the battlefield: its level is 0
{t} Level {3} (Increase it's level by 1)
When this card enters the battlefield create a 0/10 Music box artefact creature for the opponent
with Wall, "{t} tap one of your creatures this card gets +0/+2" and "End of turn: this card gets -0/-1"
If this music box leaves the battlefield this card becomes an artefact creature
If the music box leaves the battlefield and this creature is level 20 you win the game.