Ashiok's Reaper + Mortuary + Phyrexian Altar + Hypnotic Siren

Ashiok's Reaper

Mortuary

Phyrexian Altar

Hypnotic Siren

How it works

1. Activate Phyrexian Altar by sacrificing Hypnotic Siren, adding .
2. When Hypnotic Siren dies, Mortuary and Ashiok's Reaper trigger.
3. Resolve the Mortuary trigger, putting Hypnotic Siren on top of your library from your graveyard.
4. Resolve the Ashiok's Render trigger, causing you to draw Hypnotic Siren from your library.
5. Cast Hypnotic Siren by paying .
6. Repeat.

This clever loop relies on Hypnotic Siren being cast for its cheap alternative cost when it's not attached, allowing you to continually recast it after sacrificing it to Phyrexian Altar for mana. As the Siren hits the graveyard, Mortuary intercepts it to place it right back on top of your library, perfectly setting up the card draw provided by Ashiok's Reaper whenever an enchantment is put into a graveyard from the battlefield. Because the Siren falls off and becomes an enchantment creature upon dying, its journey feeds the Reaper's trigger while the Altar refunds the mana needed to start the whole cycle anew.