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The mixture of stone and crystal making up Ontrum's body gives it immense defensive and offensive strength. It crunches on most stones and gems for food, but hoards any diamonds it finds to decorate its den.

Thanks to its gargantuan jaws, which could shred thick metal plates as if they were paper, it was invincible in the ancient world it once inhabited. There is a magnet in its brain that prevents an Ontrum from losing direction while tunneling.