Gralens at Monster-Control HQ asks you to investigate reports of an unknown huge silhouette in the Depths.
Quest Location
If you have completed WANTED: Molduga, WANTED: Hinox, and WANTED: Stone Talus, you can start this quest by talking to Gralens in the Emergency Shelter in Lookout Landing, and ask him about the unknown huge silhouette.
How to Complete the Quest
You can go southeast from Nisoij Lightroot to reach the quest destination. See Camera Work in the Depths for directions to Nisoij Lightroot. However, you may wish to visit Nihcayam Lightroot, Netinet Lightroot, and Stakijat Lightroot prior to the battle so that the area with the quest destination will be lit up. These lightroots are in the same positions as Mayahcin Shrine, Teniten Shrine, and Tajikats Shrine on the surface.
At the quest destination, you find a Frox. To defeat the Frox, keep your distance and wait for it to draw a breath, then throw a bomb flower at it. It will swallow the bomb flower, which will explode, stunning it. You can then run onto its back and hit the Zonaite deposits on its back to damage it. If you stay on its back, it eventually will launch you into the air. This gives you the chance to shoot a bomb flower into its mouth, or shoot at the Zonaite deposits on its back with a bomb flower. Otherwise, if you are on the ground and the Frox looks like it is going to dash toward you or jump onto you, try to run to the side to dodge it.
After you defeat it, talk to Gralens and tell him that you hunted the huge silhouette.
Quest Reward
Gralens gives you 100 rupees. If you have also completed Unknown Sky Giant and Unknown Three-Headed Monster, Gralens gives you a Diamond.