Activate Sneak Attack by paying {R}, putting Immortal Phoenix from your hand onto the battlefield.
Activate Phyrexian Altar by sacrificing Immortal Phoenix, adding {R}.
Immortal Phoenix dies, returning itself from your graveyard to your hand.
Repeat.

Infinite death triggers

Infinite creature ETB

Infinite creature LTB

Infinite creature sacrifice triggers

Immortal Phoenix

Sneak Attack

Phyrexian Altar

Activate Sneak Attack by paying {R}, putting Immortal Phoenix from your hand onto the battlefield.
Activate Thermopod's second ability by sacrificing Immortal Phoenix, adding {R}.
Immortal Phoenix dies, returning itself from your graveyard to your hand.
Repeat.

Thermopod

Cast Immortal Phoenix.
Endrek Sahr triggers, creating six 1/1 Thrull tokens.
Sacrifice Immortal Phoenix and 6 Thrull tokens for {5}{R}{R}.
Immortal Phoenix returns to your hand.
Repeat.

Infinite colored mana

Infinite storm count

Endrek Sahr, Master Breeder

Cast Rancor by paying {G}, attaching it to Immortal Phoenix.
When Rancor enters the battlefield, Composer of Spring triggers.
Holding priority, activate Phyrexian Altar by sacrificing Immortal Phoenix, adding {G}.
When Immortal Phoenix dies, it and Rancor trigger.
Resolve the Rancor trigger, returning it to your hand from the battlefield.
Resolve the Immortal Phoenix trigger, returning it to your hand from the battlefield.
Resolve the Composer of Spring ability from step 2, putting Immortal Phoenix onto the battlefield from your hand.
Repeat.

Combos with "Immortal Phoenix"