How can you create a combo with Mikaeus, the Unhallowed, Putrid Goblin, Altar of Dementia?
user
[START OF COMBO]This combo can be formed with Mikaeus, the Unhallowed, Putrid Goblin, Altar of Dementia

Color identity: B
Mana cost: 
Steps:
  1. Activate Altar of Dementia by sacrificing Putrid Goblin.
  2. Putrid Goblin dies, triggering its persist and undying abilities.
  3. Resolve the persist trigger, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
  4. Resolve the undying trigger, doing nothing.
  5. Resolve the Altar of Dementia ability, causing target player to mill cards equal to Putrid Goblin's power.
  6. Activate Altar of Dementia by sacrificing Putrid Goblin.
  7. Putrid Goblin dies, triggering its undying ability, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
  8. Resolve the Altar of Dementia ability, causing target player to mill cards equal to Putrid Goblin's power.
  9.  Activate Altar of Dementia by sacrificing Putrid Goblin.
  10. Putrid Goblin dies, triggering its persist ability, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
  11. Repeat from step 5.[END OF COMBO STEPS]

Result:
  - Infinite +1/+1 counters on Altar of Dementia
  - Infinite death triggers
  - Infinite enters the battlefield
  - Infinite leaves the battlefield
  - Infinite sacrifice triggers[END OF COMBO RESULT][END OF COMBO]

Other prerequisites:
  - All permanants must be on the battlefield
[END OF COMBO PREREQUISITES]
assistant