Kaya's Ghostform + Brotherhood Outcast + Phantom Train

Kaya's Ghostform

Brotherhood Outcast

Phantom Train

How it works

1. Activate Phantom Train by sacrificing Brotherhood Outcast.
2. When Brotherhood Outcast dies, Kaya's Ghostform triggers, returning Brotherhood Outcast from your graveyard to the battlefield.
3. When Brotherhood Outcast enters the battlefield, it triggers, returning Kaya's Ghostform from your graveyard to the battlefield attached to Brotherhood Outcast.
4. Resolve the Phantom Train ability.
5. Repeat.

This crafty little loop relies on an infinite recursive tango between Brotherhood Outcast and Kaya's Ghostform, where every iteration starts by sacrificing the Outcast to Phantom Train to pump up the locomotive with a +1/+1 counter. As Brotherhood Outcast hits the graveyard, Kaya's Ghostform triggers to bring it right back to the battlefield, which in turn causes the Outcast's own enters-the-battlefield ability to pluck Kaya's Ghostform out of the graveyard and reattach it, seamlessly resetting the trap. Because Phantom Train accepts any artifact or creature sacrifice to fuel its growth and animate itself into a Spirit, feeding the Brotherhood Outcast to it creates an unstoppable engine of endless leaves-the-battlefield, entry, death, and sacrifice triggers.