[Honour] Baldur's Gate 3 Netherbrain - Wet Party Build - Blood of Lathander Saved the Day

This is a series of boss fight videos featuring a "wet-based lightning" party on Honour mode:
- Sarevok: • [Honour] Baldur's Gate...
- Ansur: • [Honour] Baldur's Gate...
- Steel Watcher Titan: • [Honour] Baldur's Gate...
- Raphael: • [Honour] Baldur's Gate...
- Netherbrain (final boss): • [Honour] Baldur's Gate...
The idea of this team to play around the wet condition, which makes a target vulnerable to lightning and cold damage (x2), and together Tempest Cleric's Destructive Wrath channel divinity (maximise thunder/lightning damage rolls) this means lightning damage can do a lot of damage. For example, Chain Lightning would do 160 damage (assuming failed saving throw). 3 of the 4 characters in this team are basically lightning/cold casters, and the 4th character is a ranged single-target DPS class.
For this fight, it's the one encounter where everything went wrong, and the team was just one item away from getting team wiped. My original plan is to avoid the big fight by getting everyone invisible, and that all went according to plan until Orpheus triggered the portal (12:50) and, for reasons unknown to me still, it breaks Shadowheart's invisibility. This escalated into getting my whole team exposed, 2 of them stunned, and another 2 (Shadowheart and Gale) went down (15:28). But thanks to Blood of Lathander Shadowheart was resurrected along with Gale, and a clutched Divine Intervention turned the tide. After Shadowheart and Gale got into the portal, Netherbrain went down with a couple Chain Lightnings without further hiccups.
I'll next detail the builds for the team. Note: use bg3.wiki/ to search for items or keywords.
1. "Abjuration Wizard"
Multiclass: 1 White Draconic Bloodline Sorcerer / 2 Tempest Cleric / 9 Abjuration Wizard
Abilities: 16 int / 16 dex / 14 con
Feats: Alert / ASI
White Draconic Bloodline Sorcerer gives us Armour of Agathys, which deals cold damage when attacked by a melee enemy. This can be upcasted, and at level 6 it will do 30 cold damage, or 60 damage if wet. 2 levels of Tempest Cleric for Destructive Wrath. 9 levels of Abjuration Wizard gives us 18 stacks of Arcane Ward, and together with Warding Bond from our Lightning Cleric (below), this makes Abjuration Wizard unkillable as they will take 0 damage when hit by enemies. This character will serve as a lightning caster (mostly blasting lightning bolt or chain lightning (learned via scrolls)) and frontline tank.
2. "Lightning Sorcerer"
Multiclass: 2 Tempest Cleric / 10 Storm Sorcerer
Abilities: 16 cha / 16 dex / 14 con
Feats: Alert / ASI
A pretty straightforward build. We will miss Chain Lightning with this setup, but that can be fixed by giving them Markoheshkir, which will grant Chain Lightning once per short rest.
3. "Lightning Cleric":
Multiclass: 11 Tempest Cleric / 1 Wizard
Abilities: 16 wis / 16 int / 14 dex
Feats: Alert / ASI
Tempest Cleric will get Call Lightning, and that will be the main lightning spells they'll be using, until we get to level 12 and pick up 1 level of Wizard, which they can then learn Chain Lightning through scrolls. This character will also function as a support, providing a whole host of amazing Cleric spells (e.g. Guidance, Enhance Ability, Warding Bond, Restoration spells, Spirit Guardian, Planar Ally and Heroes' Feast).
4. "Archer"
Multiclass: 5 Gloomstalker Ranger / 4 Champion Fighter / 3 Thief
Abilities: 16 dex / 16 wis / 14 con
Feats: Sharpshooter / Alert or ASI
This character makes up for the lack of single target DPS in the team. Classic combo - I prefer Thief over Assassin because because I'm dual wielding hand crossbows. The fighter side gives us action surge. In terms of itemisation, use Ne'er Misser as the main-hand weapon - it does Force damage which is much better than piercing (not many enemies have Force resistance). Any good cross-bow will work for the off-hand. Other good items include Risky Ring, Caustic Band and Coldbrim Hat. The hat, in particular, is very synergistic for the team, as it would make enemies hit by the archer have disadvantage on dexterity saving throws, which means they are much less likely to save against our lightning spells.
Level progression:
- Level 1-4: There isn't really any good lightning or cold spells, so the team won't be amazing. I mostly rely on Ice Knife as my main source of damage for the casters. During this period, the team will be carried mostly by Archer, who should go full rogue with Titanstring Bow and Strength Elixirs at this point. With this they can solo most fights with a bit of kiting. At this point everyone should be single class.
- Level 5-8: Start taking tempest cleric for the casters. At 5 we get Lightning Bolt or Call Lightning so the team is online. For archer respec them into 5 Gloomstalker / 3 Thief now.
- Level 9+: Continue leveling up the casters on their main class. Archer will get the Fighter levels.