Gelberus is one of the four High Krawl. He first introduces himself on Nessa, but you battle him on Hyoga, a frozen planet in the Fubuki system. The property of Gelberus is Corona, so use Flash Spectrobes, like Kibatekka or Isadora (both are Secret Spectrobes). When you battle him, he will change form and shoots fire at you, and will also summon small, fireball-like, Krawl that will attack you. If you get too close, he will slam the ground and fire will appear.