Spelunkk is the third planet in Spore Hero Arena, which was scorched and burned by a passing star, so all the inhabitants had to live in the underground. There are underground lakes and rivers, and also glowing crystals and spiky plants. The inhabitants are eyeless pig creatures. There is a yellow Epic creature that is sleeping near a rock pillar. There are also 4 monoliths at the underground lake that have to be hit in a certain order.
The champion is Rocky. To get to the arena, you must go to the creature who will tell you to destroy all the inferno critter's nests. Destroy them and he will tell you to hit the rocks at the lake in this order: 2, 4, 3, 1. Do that and the path to the arena will rise. Go across the path to challenge Rocky. (You must have all 4 blue fragments).