Trickstar Corobane

Flying
When you cast Trickstar Corobane you may tap any number of Trickstar creatures you control. Each creature you tap reduces Trickstar Corobane's cost by {u/r}.
{u/r}{u/r} When a Trickstar creature you control is blocked or blocks an attack, you may discard Trickstar Corobane to double that creature's power and toughness.