Mortuary + Lithatog + Memnite + Bolas's Citadel

Mortuary

Lithatog

Memnite

Bolas's Citadel

How it works

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

This clever loop relies on Bolas's Citadel to let you cast spells directly from the top of your library for life instead of mana, turning Memnite's zero mana value into a free investment of zero life. Whenever you sacrifice Memnite to Lithatog's activated ability, Mortuary immediately catches the creature as it hits the graveyard and tucks it right back onto the top of your library. Because the Citadel already grants you permission to play cards from that very spot, you can endlessly recast Memnite, feed it back to Lithatog, and repeat the cycle to generate infinite sacrifices, enter-the-battlefield triggers, and a massively pumped Lithatog.