Colfenor, the Last Yew | Sifter of Skulls | Walking Ballista

Cards

Cast
Walking Ballista by paying ({0} magic symbol) .
Walking Ballista enters the battlefield and dies as a state-based action due to having zero or less toughness.
Colfenor and
Sifter of Skulls trigger.
Resolve the
Colfenor trigger, returning nothing from your graveyard to your hand.
Resolve the
Sifter of Skulls trigger, creating a 1/1 Eldrazi Spawn creature token.
Activate the Eldrazi Spawn by sacrificing it, adding ({C} magic symbol) .
The Eldrazi Spawn dies, triggering
Colfenor, returning
Walking Ballista from your graveyard to your hand.
Repeat.
Once you have a large amount of ({C} magic symbol) , you may cast
Walking Ballista using an arbitrarily large amount of mana, then use its ability to deal infinite damage to any target(s).