Kindred Trap

This spell costs {0} to cast if there are five or more creatures of the same type onto the battlefield.
Choose a creature type. Until end of turn, each
creature you control is of the chosen type in
addition to its other types. Until end of turn,
each creature you control of the chosen type has
''{t}: Destroy target creature of the chosen type
you don't control, then put a +1/+1 counter on
each creature of the chosen type you control.''