Mirror-Force Barrier

Defender (This creature can't attack.)
Shroud (This creature can't be the target of spells or abilities.)
Whenever Mirror-Force Barrier is dealt combat
damage by a creature it blocks, it deals {x} damage
to that creature where {x} is Mirror-Force
Barrier's toughness. Any damage dealt this
way in excess of that creature's toughness is dealt
to that creature's controller instead.