Mello, the Puzzling

Shadow, Hexproof
{3}{u}{u}: Crew this vehicle.
When Mello, the Puzzling enters or attacks,
put a shadow counter on target creature you control that does not have shadow. If you cannot do this, shuffle Mello, the Puzzling into its owners library.
Creatures with shadow you control gain "Whenever this creature deals combat damage to an opponent, tap target creature and put a stun counter on it."