Shadowspear and Lich's Mastery on the battlefield.
You have a way to cause Lich's Mastery to leave the battlefield.
({3} magic symbol) ({R} magic symbol) available.
Steps
Cast Harmless Offering by paying ({2} magic symbol) ({R} magic symbol) , giving an opponent control of Lich's Mastery.
If needed, activate Shadowspear by paying ({1} magic symbol) , causing all permanents your opponents control to lose hexproof and indestructible until end of turn.
Cause Lich's Mastery to leave the battlefield.
Lich's Mastery triggers, causing its controller to lose the game.