The Skullspore Nexus (Promo Pack) [The Lost Caverns of Ixalan Promos]

This spell costs X less to cast, where X is the greatest power among creatures you control.

Whenever one or more nontoken creatures you control die, create a green Fungus Dinosaur creature token with base power and toughness each equal to the total power of those creatures.

2, T: Double target creature's power until end of turn.