Cast Skull Skaab by paying {0}.
When Skull Skaab enters the battlefield, it triggers, causing you to sacrifice it.
When Skull Skaab dies, Enduring Renewal triggers, returning it to your hand from your graveyard.
Repeat.

Infinite death triggers

Infinite ETB

Infinite LTB

Infinite sacrifice triggers

Infinite storm count

Rooftop Storm

Enduring Renewal

Skull Skaab

Cast Skull Skaab either from your hand or from the top of your library by paying {0}.
When Skull Skaab enters the battlefield, its exploit ability triggers, causing you to sacrifice it.
When Skull Skaab dies, Mortuary triggers, putting it on top of your library from your graveyard.
Repeat.

Mortuary

Realmwalker

Combos with "Skull Skaab"