Tablet of the Guilds triggers, causing you to gain life.
When Acererak enters, its first ability and Carnival of Souls trigger.
Resolve the Carnival of Souls trigger, causing you to add and lose 1 life.
Resolve the Acererak trigger, returning it from the battlefield to your hand, and venturing into Lost Mine of Phandelver.
Repeat.
This clever loop revolves around casting Acererak the Archlich over and over, taking advantage of the fact that its entry ability bounces it right back to your hand as long as you steer clear of the Tomb of Annihilation. Carnival of Souls plays a crucial role by turning every single one of those entries into a refunded black mana while offsetting the life cost with Tablet of the Guilds, which gains you life whenever you cast the black-and-blue lich. Meanwhile, Hamza, Guardian of Arashin acts as a powerful cost reducer—though its static discount isn't strictly required to keep the black-neutral loop going, it can help discount the casting cost if you ever need to pivot or help set up the board. By repeatedly bouncing Acererak, you trigger your dungeon ventures endlessly to reap all the treasures, tokens, and resources you could ever want.