Omoroth the Sea Titan Scanner海の巨獣オモロスのスキャナー

Scans the world for Omoroth the Sea Titan. Consumed on successful scan.
In-game description

How to use Omoroth the Sea Titan Scanner

Omoroth the Sea Titan Scanner is a scanner that marks where Omoroth the Sea Titan is on your map. Use it when you cannot find the boss.

Put Omoroth the Sea Titan Scanner in your hotbar, select it and use it (right-click). Using it takes 2 seconds.
If the scan succeeds, the location of Omoroth the Sea Titan is marked on your map and Omoroth the Sea Titan Scanner is used up (it is only consumed on a successful scan).
Follow the marker on the map.

The marker stays on the map until Omoroth the Sea Titan is defeated.

Calculated and summarized by this site from the game data (1.3.0.6).

Material	Amount	How to get the material
Ancient Gemstone	× 10	Fishing Boss Enemy Chest Breakable
Mechanical Part	× 10	Boss Enemy Chest Digging Breakable
Sea Shell	× 10	Enemy Breakable