Core Keeper

Ghorm the Devourer is a giant larva that travels in a circle around the Clay Caves and the Forgotten Ruins. Usually the second boss that you fight.

Defeating Ghorm drops Ghorm's Horn, an item required for progression.

This boss spawn and do a complet circle of the map at 230 tiles from the core.
To kill him you need him to stop circling the map and start attacking you for that you need to deal about 1000 damage before he go to far like 50 tiles and recover is full health. The best way to do it is to use some trap any type will do the trick just put 5 line of traps in the middle of is path and he should take 1/4 of is health. After that the boss will start attacking by rushing you in straight line faster and faster. He will transforms any ground that he touch into slime gelly ground that slow you down. And he can one shot anywall so dont think about camping.
If you dont have any trap you can also use 5 bomb but it cost more.
Good luck.