How can you create a combo with Lagrella, the Magpie, Karmic Guide, Preston, the Vanisher, Momentary Blink?
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[START OF COMBO]This combo can be formed with Lagrella, the Magpie, Karmic Guide, Preston, the Vanisher, Momentary Blink

Color identity: GWU
Mana cost: {1}{W}
Steps:
  1. Cast Momentary Blink by paying {1}{W}, blinking Lagrella.
  2. When Lagrella enters the battlefield, it and Preston triggers.
  3. Resolve the Lagrella trigger, exiling Karmic Guide until Lagrella leaves the battlefield.
  4. Resolve the Preston trigger, creating a token copy of Lagrella that is a 0/1 Illusion.
  5. Put the nontoken Lagrella into your graveyard due to the legend rule.
  6. If Lagrella is your commander, choose not to return it to the command zone from your graveyard.
  7. When Lagrella leaves the battlefield, Karmic Guide is returned to the battlefield from exile.
  8. Karmic Guide, Lagrella and Preston each trigger.
  9. Resolve the Preston trigger, creating a token copy of Karmic Guide that is a 0/1 Illusion.
  10. When the Karmic Guide token enters the battlefield, it triggers, choosing to return nothing to the battlefield.
  11. Resolve the Lagrella trigger, putting two +1/+1 counters on the nontoken Karmic Guide.
  12. Resolve the Karmic Guide trigger from step 8, returning Lagrella from your graveyard to the battlefield.
  13. Repeat from step 2.[END OF COMBO STEPS]

Result:
  - Infinite creature tokens
  - Infinite death triggers
  - Infinite enters the battlefield
  - Infinite leaves the battlefield[END OF COMBO RESULT][END OF COMBO]

Other prerequisites:
  - Lagrella, the Magpie must be on the battlefield
  - Karmic Guide must be on the battlefield
  - Preston, the Vanisher must be on the battlefield
  - Momentary Blink must be in your hand
[END OF COMBO PREREQUISITES]
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