Title: Baldur's Gate 3 - Grym, Eternal Protector of the Forge
Description:
Grym is an Adamantine Golem and the protector of the adamatine forge in the Grymforge in the Underdark. Now we know where the name "Grymforge" comes from.

If the Adamantine Forge is used, Grym will activate and attempt to destroy its users. Since I wanted to craft some equipment, I had to deal with Grym first.
Grym is immung against all damage, unless it stands in lava. The best way to defeat the golem is to use ranged attacks from the opposite site of the forge. Grym always tries to attack the last enemy who attacked it.
You have to lure Grym in the middle of the forge to stand under the hammer. And then activate the hammer, which will deal lots of damage to Grym. Repeat until Grym is defeated. Afterwards the forge can be safely used without any interruption.
Link: https://www.digioso.org/bg3_grym