Cause a permanent to enter the battlefield under your control.
Eutropia triggers, putting a +1/+1 counter on Herd Baloth.
Herd Baloth triggers, creating a 4/4 Beast creature token that is also an enchantment due to Enchanted Evening.
Repeat from step 2.

Infinite +1/+1 counters on a creature

Infinite creature tokens

Infinite creature ETB

Eutropia the Twice-Favored

Herd Baloth

Enchanted Evening

Cause a permanent to enter the battlefield under your control.
Eutropia triggers, putting a +1/+1 counter on Scurry Oak.
Scurry Oak triggers, creating a 1/1 Squirrel creature token that is also an enchantment due to Enchanted Evening.
Repeat from step 2.

Scurry Oak

Cast Rancor by paying {G}, attaching it to any other creature you control.
When Rancor enters the battlefield, Eutropia triggers, putting a +1/+1 counter on Herd Baloth.
Herd Baloth triggers, creating a 4/4 Beast creature token.
Activate Phyrexian Altar by sacrificing the creature with Rancor attached, adding {G}.
Rancor triggers, returning it from your graveyard to your hand.
Repeat.

Infinite death triggers

Infinite creature LTB

Infinite creature sacrifice triggers

Infinite storm count

Rancor

Phyrexian Altar

Cast Rancor by paying {G}, attaching it to any other creature you control.
When Rancor enters the battlefield, Eutropia triggers, putting a +1/+1 counter on Scurry Oak.
Scurry Oak triggers, creating a 1/1 Squirrel creature token.
Activate Phyrexian Altar by sacrificing the creature with Rancor attached, adding {G}.
Rancor triggers, returning it from your graveyard to your hand.
Repeat.

Combos with "Eutropia the Twice-Favored"