Brotherhood Outcast + Phyrexian Altar + Shade's Form

Brotherhood Outcast

Phyrexian Altar

Shade's Form

How it works

1. Activate Phyrexian Altar by sacrificing Brotherhood Outcast.
2. When Brotherhood Outcast dies, Shade's Form triggers, returning Brotherhood Outcast from your graveyard to the battlefield.
3. When Brotherhood Outcast enters the battlefield, it triggers, returning Shade's Form from your graveyard to the battlefield attached to Brotherhood Outcast.
4. Repeat.