Elemental Mastery + Black Carriage

Elemental Mastery
Black Carriage

Requires
Elemental Mastery must be on the battlefield. Black Carriage must be on the battlefield. Elemental Mastery attached to Black Carriage.
Steps
  1. During your upkeep, activate Black Carriage by tapping it, creating at least four 1/1 Elemental creature tokens.
  2. Activate Black Carriage by paying 0 and sacrificing an Elemental token, untapping Black Carriage.
  3. Repeat.
Results
Infinite creature tokens with haste. Infinite ETB.