Pelting Pebble

Indestructible
{t} an untapped creature you control and deal {x} damage to another target creature, where {x} is equal to the casting cost of the creature tapped. If the creature is controlled by another player, that player gains control of Pelting Pebble.
If Pelting Pebble leaves the battlefield for any reason, then shuffle Pelting Pebble back into the owner's library.