Lagrella, the Magpie + Karmic Guide + Preston, the Vanisher + Flicker

Lagrella, the Magpie

Karmic Guide

Preston, the Vanisher

Flicker

How it works

1. Cast Flicker by paying 1, blinking Lagrella.
2. When Lagrella enters the battlefield, it and Preston triggers.
3. Resolve the Lagrella trigger, exiling Karmic Guide until Lagrella leaves the battlefield.
4. Resolve the Preston trigger, creating a token copy of Lagrella that is a 0/1 Illusion.
5. Put the nontoken Lagrella into your graveyard due to the legend rule.
6. If Lagrella is your commander, choose not to return it to the command zone from your graveyard.
7. When Lagrella leaves the battlefield, Karmic Guide is returned to the battlefield from exile.
8. Karmic Guide, Lagrella and Preston each trigger.
9. Resolve the Preston trigger, creating a token copy of Karmic Guide that is a 0/1 Illusion.
10. When the Karmic Guide token enters the battlefield, it triggers, choosing to return nothing to the battlefield.
11. Resolve the Lagrella trigger, putting two +1/+1 counters on the nontoken Karmic Guide.
12. Resolve the Karmic Guide trigger from step 8, returning Lagrella from your graveyard to the battlefield.
13. Repeat from step 2.

This loop uses Flicker to kick-start a self-sustaining cycle where Lagrella, the Magpie continually exiles and returns Karmic Guide from the graveyard. Meanwhile, Preston, the Vanisher acts as our magical foundry, watching each non-cast creature enter to churn out an endless army of token copies of both Lagrella and Karmic Guide. By leaning on the legend rule to reset our original Lagrella into the graveyard, Karmic Guide's enter-the-battlefield ability steps in to resurrect her every single iteration.