Doran, Besieged by Time

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.

Bark of Doran

Equipped creature gets +0/+1.
As long as equipped creature's toughness is greater than its power, it assigns combat damage equal to its toughness rather than its power.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)