At the beginning of your upkeep, Mayael's Aria triggers.
Holding priority, cast March of the Multitudes with X=5 by tapping Devilish Valet and by paying at most ({4} magic symbol) ({G} magic symbol) ({W} magic symbol) ({W} magic symbol) , creating five 1/1 Soldier creature tokens.
When the Soldiers enter the battlefield, Devilish Valet triggers five times, doubling its power five times, causing its power to be at least 32 until end of turn.
Resolve the Mayael's Aria trigger, causing you to put a +1/+1 counter on each creature you control, gain 10 life and win the game.