Mortuary + Harvester of Souls + Chamber Sentry

Mortuary

Harvester of Souls

Chamber Sentry

How it works

1. Cast Chamber Sentry by paying 0.
2. Chamber Sentry enters and dies as a state-based action due to having 0 toughness, triggering Mortuary and Harvester of Souls.
3. Resolve the Mortuary trigger, putting Chamber Sentry from your graveyard onto the top of your library.
4. Resolve the Harvester of Souls trigger, causing you to draw a card, thus drawing Chamber Sentry from your library.
5. Repeat.

This elegant loop relies on casting Chamber Sentry for zero mana so that state-based actions immediately send it to the graveyard, setting off a cascade of triggers. Mortuary catches the creature as it hits the graveyard, neatly placing it back on top of your library, while Harvester of Souls capitalizes on that very death to let you draw it right back into your hand. Because Chamber Sentry's color requirements are met with zero mana of all five colors, you can repeat this process endlessly to fuel infinite enters-the-battlefield effects, leave-the-battlefield triggers, deaths, and draws.