Mr. X, Bio Weapon

Indestructible, protection from zombies

Whenever Mr. X, Bio Weapon enters the battlefield, choose a player. Until that player dies, Mr. X, may only attack that player, and attacks each turn if able.

Whenever Mr. X, Bio Weapon attacks, create a 1/1 zombie creature token that's also tapped and attacking. At your end step, if a zombie you control dealt damage to a player this turn, put a +1/+1 counter on Mr. X, Bio Weapon.