The Two-Faced Troll

As long as your life total is more than
half your starting life total, spells you cast
cost {r}{g} less to cast and The Two-Faced Troll has Vigilance.
As long as your life total is less than or equal
to half your starting life total, spells you cast cost {b}{b} less to cast, and The Two-Faced Troll has Deathtouch and Defender.