Catasthea, the Roiling Sky

This spell costs {x} less to cast, where X is the
amount of of noncombat damage dealt to players
or planeswalkers by sources you control this turn.
Flying, trample, prowess
Whenever you cast an instant or sorcery spell,
counter that spell. If this is the third time this
ability has resolved this turn, Catasthea, deals
damage equal to its power to any target.