Once you arrive in the Grymforge portion of the Underdark in Baldur's Gate 3, you'll quickly determine that you should find a way to free Nere before you leave. He's another one of the Absolute's True Souls, trapped behind a cave-in and close to inhaling a lethal quantity of poison.
Saving (and then killing) Nere is one of the ways you can acquire a moonlantern to make your way to Moonrise Towers. If you've chatted with the mushroom folks at the Myconid Colony, you can also bring Nere's head to them in return for a reward.
