They are made of different coloured rock and crystals. There are five different kinds of Rock Monster. The rock monsters are Meltrox, Boulderax, Glaciator, Sulfurix, and Firox. Meltroxes are red, and are apparently always angry. The yellow ones, Sulfurixes, are more intelligent and can melt tunnels through solid rock. Apparently, all of the Rock Monsters are afraid of the blue Glaciators. The Glaciators are shown to have ice powers. The green ones are Boulderaxes which are strong, slow, but not intelligent, and often attempt to destroy the Power Miners' vehicles. The orange ones are Firoxes which are extremely fast, sneaky, and love to play tricks.
They are shown to have some primitive technology, like catapults. The Rock Monsters eat crystals, which give them power. If a rock monster eats a different coloured crystal to what it is it will burp and break wind, according to the video released by LEGO Club TV on YouTube. If they consume dynamite (and it goes off in the stomach) they will apparently solidify.
a new type of larger Rock Monster was released. They appear to be larger versions of the small monsters. The large version of Sulfurix is called Geolix, while the large version of Meltrox is Tremorox. As well as those, another rock monster called the Crystal King or Rock Rage is the biggest Rock Monster. He is now awoken from his sleep.
- The Rock Monsters make their appearance in Princess Twivine Rises!