Mayael's Aria + Jumbo Cactuar + Shadow of the Second Sun

Mayael's Aria

Jumbo Cactuar

Shadow of the Second Sun

How it works

1. Declare Jumbo Cactuar as an attacker, triggering its ability, giving it +9999/+0 until end of turn.
2. At the beginning of your postcombat main phase, Shadow of the Second Sun triggers, causing you to get an additional beginning phase after this phase.
3. During the beginning phase's upkeep step, Mayael's Aria triggers, causing you to put a +1/+1 counter on each creature you control, gain 10 life, and win the game.