How can you create a combo with Ob Nixilis, Unshackled, Field of Ruin, Rings of Brighthearth, Crucible of Worlds?
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[START OF COMBO]This combo can be formed with Ob Nixilis, Unshackled, Field of Ruin, Rings of Brighthearth, Crucible of Worlds

Color identity: B
Mana cost: {8}
Steps:
  1. Activate Field, targeting a land and triggering Rings of Brighthearth.
  2. Pay to copy the Field effect, targeting a different land.
  3. Resolve both triggers and the resulting Ob Nixilis triggers, forcing all opponent to lose 20 life.
  4. Use Crucible of Worlds to play Field.
  5. Repeat steps 1-3.[END OF COMBO STEPS]

Result:
  - Each opponent loses 40 life[END OF COMBO RESULT][END OF COMBO]

Other prerequisites:
  - All permanants must be on the battlefield
  - You must have a land drop available.
  - Four nonbasic lands under opponents' control.
[END OF COMBO PREREQUISITES]
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