How can you create a combo with River Kelpie, Mikaeus, the Unhallowed, Phyrexian Altar?
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[START OF COMBO]This combo can be formed with River Kelpie, Mikaeus, the Unhallowed, Phyrexian Altar

Color identity: UB
Mana cost: 
Steps:
  1. Activate Phyrexian Altar by sacrificing River Kelpie, adding {1}.
  2. River Kelpie's persist and undying abilities trigger.
  3. Resolve the persist trigger, returning River Kelpie from your graveyard to the battlefield with a -1/-1 counter on it.
  4. River Kelpie enters the battlefield, causing you to draw.
  5. The undying trigger fails to resolve because River Kelpie is not in your graveyard.
  6. Activate Phyrexian Altar by sacrificing River Kelpie, adding {1}.
  7. River Kelpie's undying and persist abilities trigger.
  8. Resolve the undying trigger, returning River Kelpie from your graveyard to the battlefield with a +1/+1 counter on it.
  9. River Kelpie enters the battlefield, causing you to draw a card.
  10. The persist trigger fails to resolve because River Kelpie is not in your graveyard.
  11. Repeat.[END OF COMBO STEPS]

Result:
  - Infinite card draw
  - Near-infinite colored mana
  - Near-infinite death triggers
  - Near-infinite enters the battlefield
  - Near-infinite leaves the battlefield
  - Near-infinite sacrifice triggers[END OF COMBO RESULT][END OF COMBO]

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