Doran, Besieged by Time

Legendary Creature — Treefolk Druid

Each creature spell you cast with toughness greater than its power costs less to cast. Whenever a creature you control attacks or blocks, it gets +X/+X until end of turn, where X is the difference between its power and toughness.

"Each year that passes rots you with scars. Shelter your heart, for the world is cruel."