Gusher

When a creature called Pacer is summoned under
your control, you may reveal this from your hand
and destroy that Pacer under your control, and if
you do, you may cast this without paying its
mana cost, and as if it had Flash.
Defender
{t}: Deal X damage to target attacking or blocking
creature, where X is Gusher's power. If tapped
from this ability, this can still block as if it was
untapped.