Nearheath Stalker dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Resolve the
Altar of Dementia ability.
Activate
Altar of Dementia by sacrificing
Nearheath Stalker.
When
Nearheath Stalker dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
Nearheath Stalker 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
Altar of Dementia ability from step 4.
Repeat from step 4.
Notes
If
Nearheath Stalker 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 mill.
Infinite creature sacrifice triggers.
Infinite self-mill.
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.