Onyx agate is a trinket in TBoI: Regambled, a mod for The Binding of Isaac.

UNCOMMON | Base price: 7 coins

This Joker is only available while playing as Jimbo or Tainted Jimbo.

Jimbo:
Club cards give +0.08 damage when scored.
Club cards' explosions are more frequent, bigger and deal more damage.

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Tainted Jimbo: Same effect as base game.

• Check out the trinket description on the mod's external Wiki.
• Download TBoI: Regambled from the Steam Workshop.