Activate Araumi by tapping it and exiling three cards from your graveyard, giving Gray Merchant encore until end of turn.
Activate Gray Merchant's encore ability by paying ({3} magic symbol) ({B} magic symbol) ({B} magic symbol) and exiling it from your graveyard, creating at least three token copies of it with haste.
The Gray Merchants enter the battlefield, triggering their abilities twice each.
Resolve the first Gray Merchant ability, causing each opponent to lose at least 8 life and you to gain at least 8 life.
Repeat step 4 for each remaining Gray Merchant trigger.