Rainbow Crystals in The Forge on Roblox are obtained by unlocking the Goblin Cave in the Forgotten Kingdom, then mining the crystal nodes inside until one rolls Rainbow Crystal at a very low rate. The commonly reported drop chance is about 1 in 5,000 from crystal mining, so expect a grind.

How to get them

  1. Reach the Forgotten Kingdom and find the Goblin King area.
  1. Complete the Goblin King questline to get the key that opens the Goblin Cave.
  1. Go inside the cave and mine the glowing crystal nodes, not just the plain rocks.
  1. Keep mining until a Rainbow Crystal appears; it can come from the cave’s crystal nodes, but the chance is extremely low.

Fast farming tips

  • Use luck boosts if you have them, such as Luck Potions or other luck bonuses.
  • Pick a low-population or private server so nodes are easier to cycle.
  • Mine all available crystal nodes, then move on if the drop is not rainbow and let them respawn.
  • Don’t keep hitting a crystal after the loot appears; several guides say to stop and move on so you can reset the node faster.

Practical expectation

This is a rare drop, so the real strategy is repetition rather than a special hidden trick. Some guides describe a loop of clearing every crystal cluster in the Goblin Cave, then repeating the route until RNG favors you.

Note

The information above is for The Forge , which is what the available public guides point to for “rainbow crystals” on Roblox.

Need a shorter step-by-step route from the spawn point to the Goblin Cave?