Mortuary + Goblin Bombardment + Bolas's Citadel + Kobolds of Kher Keep

Mortuary

Goblin Bombardment

Bolas's Citadel

Kobolds of Kher Keep

How it works

1. Activate Goblin Bombardment by sacrificing Kobolds of Kher Keep
2. When Kobolds of Kher Keep dies, Mortuary triggers, putting Kobolds of Kher Keep from your graveyard onto the top of your library.
3. Resolve the Goblin Bombardment ability.
4. Cast Kobolds of Kher Keep from the top of your library by paying 0 life.
5. Repeat.

This loop achieves infinite damage and death triggers by recycling a creature with a mana value of zero—Kobolds of Kher Keep—directly from the graveyard back to the top of your library via Mortuary every time you sacrifice it to Goblin Bombardment. Normally, playing it repeatedly from the top of your library would be constrained by the usual timing rules, but Bolas's Citadel solves this by letting you cast spells from the top of your library at any time. Because Kobolds of Kher Keep costs zero mana, Bolas's Citadel requires zero life to cast it, allowing you to execute this sacrifice-and-recast sequence infinitely without running out of resources.