Young Wolf dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Resolve the
Umbral Collar Zealot ability.
Activate
Umbral Collar Zealot by sacrificing
Young Wolf.
When
Young Wolf dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
Young Wolf enters and dies as a state-based action due to having 0 toughness. Its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Resolve the
Umbral Collar Zealot ability from step 4.
Repeat from step 4.
Notes
If
Young Wolf starts with a +1/+1 counter on it, then you may start the combo from step 4 instead.
Results
Infinite creature ETB.
Infinite creature LTB.
Infinite death triggers.
Infinite creature sacrifice triggers.
Infinite surveil.
Metadata
Bracket tag
SpicyBracket 3-4+
Probably 3 or 4, but hard to classify
1
2
3
4
5
1 · Exhibition5 · cEDH
Bracket tags are estimated from the cards and results of each combo, as a guideline rather than a strict classification.