Doran, Besieged by Time is a rare Legendary Creature — Treefolk Druid card from Lorwyn Eclipsed (ECL), collector number 334. Current market price: $1.60 (foil $3.90), TCGplayer market prices via Scryfall.
Each creature spell you cast with toughness greater than its power costs {1} 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.