Mortuary + Blasting Station + Bolas's Citadel + Willow Geist

Mortuary

Blasting Station

Bolas's Citadel

Willow Geist

How it works

1. Activate Blasting Station by tapping it and sacrificing Willow Geist.
2. When Willow Geist dies, it and Mortuary triggers.
3. Resolve the Mortuary trigger, putting Willow Geist from your graveyard onto the top of your library.
4. Resolve the Willow Geist trigger, causing you to gain 1 life.
5. Resolve the Blasting Station ability.
6. Cast Willow Geist from the top of your library by paying 1 life due to Bolas's Citadel.
7. When Willow Geist enters, Blasting Station triggers, untapping Blasting Station.
8. Repeat.

This loop uses Bolas's Citadel to bypass conventional mana costs entirely, letting you cast Willow Geist straight from the top of your library by trading life instead of mana. Every time you sacrifice that same Willow Geist to Blasting Station, Mortuary steps in to instantly recycle it right back to the top of your library. Meanwhile, Willow Geist's own trigger cushions the life cost you pay to Bolas's Citadel by gaining you life when it dies, while Blasting Station untaps upon the creature's return to endlessly loop the damage.