The simplest way is to just make it wet and annihilate it with lightning spells.
- Alternatively wear it down with overtime damage like bleeding or caustic brine, death by a thousand cuts.
- Lae'zel as a Battle Master does enough damage with her unique attacks.
- Karlach with the [Everburn Blade] also does enough damage when she rolls high enough damage.
- Paladin's holy smites can also break through the shell.
- Luring it to the hook horrors near the Sussur Tree could be beneficial, I think Filro might aggro as well.