Cast Sojourner's Companion by paying {0}.
Radagast triggers, creating two 3/3 Beast creature tokens.
Activate Phyrexian Altar twice by sacrificing the Beasts, adding {1}{G}.
Activate Temur Sabertooth by paying {1}{G}, returning Sojourner's Companion from the battlefield to your hand.
Repeat.

Infinite death triggers

Infinite creature ETB

Infinite creature LTB

Infinite creature sacrifice triggers

Infinite storm count

Radagast, Wizard of Wilds

Adrix and Nev, Twincasters

Temur Sabertooth

Phyrexian Altar

Sojourner's Companion

Doubling Season

Primal Vigor

Parallel Lives

Cast Sojourner's Companion by paying {0}.
Radagast and Tangleroot trigger.
Resolve the Tangleroot trigger, adding {G}.
Resolve the Radagast trigger, creating a 3/3 Beast creature token.
Activate Phyrexian Altar by sacrificing the Beast, adding {1}.
Activate Temur Sabertooth by paying {1}{G}, returning Sojourner's Companion from the battlefield to your hand.
Repeat.

Tangleroot

Combos with "Sojourner's Companion"