Activate Ashnod's Altar by sacrificing Infernal Vessel, adding {C}{C}.
When Infernal Vessel dies, it triggers, returning itself from your graveyard to the battlefield as a Demon in addition to its other types.
Activate Ashnod's Altar by sacrificing Infernal Vessel, adding {C}{C}.
When Infernal Vessel dies, Valkyrie's Call triggers, returning Infernal Vessel from your graveyard to the battlefield as an Angel in additional to its other types.
Repeat.

Infinite creature LTB

Infinite creature ETB

Infinite creature sacrifice triggers

Infinite death triggers

Infinite colorless mana

Infernal Vessel

Valkyrie's Call

Ashnod's Altar

Activate Arcbound Ravager by sacrificing Optimus Prime, Hero.
When Optimus Prime, Hero dies, its second ability triggers, returning it from your graveyard to the battlefield as Optimus Prime, Autobot Leader.
Activate Arcbound Ravager by sacrificing Optimus Prime, Autobot Leader.
When Optimus Prime, Autobot Leader dies, Valkyrie's Call triggers, returning Optimus Prime from your graveyard to the battlefield as Optimus Prime, Hero as an Angel with flying.
Resolve both Arcbound Ravager abilities from steps 1 and 3.
Repeat.

Infinite +1/+1 counters on a creature

Optimus Prime, Hero // Optimus Prime, Autobot Leader

Arcbound Ravager

Cast the Vehicle by paying its mana cost.
When the Vehicle enters the battlefield, Simulacrum Synthesizer triggers, creating a 0/0 Construct artifact creature token that gets +1/+1 for each artifact you control.
Activate the Vehicle's crew ability by tapping the Construct, causing the Vehicle to become an artifact creature until end of turn.
Activate Ashnod's Altar by sacrificing the Vehicle.
When the Vehicle dies, Valkyrie's Call triggers, returning the Vehicle from your graveyard to the battlefield. It will not be an Angel because the Vehicle is no longer a creature and cannot gain creature types.
When the Vehicle enters the battlefield, Simulacrum Synthesizer triggers, creating a 0/0 Construct artifact creature token that gets +1/+1 for each artifact you control.
Repeat from step 3.

Infinite artifact ETB

Infinite artifact LTB

Infinite artifact sacrifice triggers

Infinite tapped creature tokens

Vehicle with MV >= 3 and a Crew Ability

Simulacrum Synthesizer

Activate Shilgengar by sacrificing Felidar Guardian.
When Felidar Guardian dies, Valkyrie's Call triggers, returning Felidar Guardian from your graveyard to the battlefield as an Angel.
When Felidar Guardian enters the battlefield, it triggers, blinking Conspiracy. Choose any creature type except "Angel" as Conspiracy enters the battlefield.
Resolve the Shilgengar ability.
Repeat.

Felidar Guardian

Conspiracy

Shilgengar, Sire of Famine

Activate Kiki-Jiki by tapping it, creating a token copy of Ruthless Technomancer with haste.
When the Ruthless Technomancer token enters the battlefield, it triggers, causing you to sacrifice Kiki-Jiki and create two Treasure tokens,
When Kiki-Jiki dies, Valkyrie's Call triggers, returning Kiki-Jiki from your graveyard to the battlefield as an Angel with flying and a +1/+1 counter on it.
Activate Kiki-Jiki by tapping it, creating a token copy of Ruthless Technomancer with haste.
When the Ruthless Technomancer token enters the battlefield, it triggers, causing you to sacrifice Kiki-Jiki and create three Treasure tokens,
Activate thee Treasure tokens by tapping and sacrificing them, adding {2}{B}.
Activate a Ruthless Technomancer by paying {2}{B} and sacrificing two Treasures, returning Kiki-Jiki from your graveyard to the battlefield.
Repeat.

Infinite creature tokens with haste

Kiki-Jiki, Mirror Breaker

Ruthless Technomancer

Activate Amoeboid Changeling's second ability by tapping it, causing another nontoken creature you control to lose all creature types until end of turn.
Activate Spawning Pit by sacrificing the creature targeted in step 1.
When the creature dies, Valkyrie's Call triggers, returning the creature from your graveyard to the battlefield as a white Angel.
When the creature enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Resolve the Spawning Pit ability.
Repeat.

Infinite charge counters on a permanent

Infinite mana creatures you control can produce

Infinite untap of creatures

Intruder Alarm

Amoeboid Changeling

Spawning Pit

Activate Amoeboid Changeling's second ability by tapping it, removing all creature types from Giant-Sized Flying Ant.
Activate Spawning Pit by sacrificing Giant-Sized Flying Ant.
When Giant-Sized Flying Ant dies, Valkyrie's Call triggers, returning Giant-Sized Flying Ant from your graveyard to the battlefield as an Angel with flying and a +1/+1 counter on it.
When Giant-Sized Flying Ant enters the battlefield, it triggers, untapping Amoeboid Changeling.
Resolve the Spawning Pit ability, putting a charge counter on it.
Repeat.

Giant-Sized Flying Ant

Combos with "Valkyrie's Call"