Baldur's Gate 3

Okay. So.

IMPORTANT NOTE: This build can work with a Durge build but requires extra steps. They will be listed.

Level 1: Draconic Sorcerer. Take whatever cold option you want but personally I'd recommend White as it gives you Armor of Agathys. You won't be using many spell slots in the game so it's worth having. This is sort of a given, but take the Ray of Frost cantrip as a Sorcerer option. You can choose whatever race you want but if you choose Ray of Frost through racial stuff this build will immediately fail as it requires the spell to be scaling off your Charisma and not another ability like Intelligence, which is what your spell will scale off of if you take it as a half-elf as an example.

Level 2+: Keep taking Sorcerer. Your metamagic options should be twinned and quickened. Other options are personal choice but Distant works well. When given the option for a Feat, take an ability score increase. Keep doing so until you have a 20 in Charisma. Hag Hair also works. You can take a Bard level very early on (Your second level) if you're so inclined but it will mess with that ASI. I usually do for extra skill bonuses or performance stuff. I would also heavily recommend taking the Haste spell when you gain access to it. As a spellcaster, you should almost always be concentrating on a spell to begin with and nothing is better for this build than perpetual Haste concentration. Although you could also slap Haste on Gale and just have him hide in the corner, boosting you and protecting himself. A third option is to twin cast Haste (such an amazing option) and slap them on Frontline, have Gale cast Haste on you, and then proceed to fucking destroy everything in a three mile radius. Also would highly recommend taking Create Water on a separate caster to increase damage.

However this build does revolve specifically around effects and items. Here is a list of those effects and items.

DURGE WARNING: One of these items requires that Tiefling bard to be alive in the Second Act of the game. As you may or may not be aware, that bard will die if you're playing Durge. To prevent her death you must sneak up behind her and knock her out. Make sure to use non-lethal damage. Magic will kill her so stick to physical attacks. Leave her there unconscious and then go meet Kagha. Once you meet Kagha, leave the grove and take a long rest. Normally at this point Alfira the Bard will drop by your camp but she's knocked out so you get the secondary NPC, Quill Grootslang, who will come to your camp during that Long Rest instead. Guide here.

Status 1 | Wet: Affected entity is immune to burning, Wild Magic: Burning, resistant to fire damage and vulnerable to cold and lightning damage.

Item 1 | Morning Frost: Continue the game as you normally would until it is time to go to either the Mountain Pass or the Underdark. We will be going to both but choose the Underdark first. Once there make it your lifes mission to get the three pieces of Morning Frost and assemble it. The benefit of Morning Frost is that it adds 1 to all cold damage and it also has the chance to apply Chilled to the target. What's Chilled you ask?

Status 2 | Chilled: Affected entity is Vulnerable to Cold damage and Resistant to Fire damage. Combining this with Wet will replace both conditions and make the target Frozen. (Sidenote but we'll get to Frozen in a bit.)

Item 2 | Winter's Clutches: Once you've got the staff, you can either continue to fuck up the Underdark or head off to the Mountain Pass and return later. In the Mountain Pass, well before the Creche, is an NPC named Lady Esther. Before you do anything else with her, go to her trading options and buy an item called Winter's Clutches. They are a set of gloves. Their benefit is that whenever you do cold damage you apply 2 turns of Encrusted with Frost.

Status 3 | Encrusted with Frost: Affected entity has disadvantage on Dexterity saving throws. When there are 7+ turns of Encrusted with Frost applied to an enemy, they must make a DC12 Con Save. On a success they take 1d4 cold damage (effected by your items/abilities). On a failure they become Frozen. The item will say otherwise but the items text is wrong. Or was. Not sure if they fixed that.

Status 4 | Frozen: Affected entity is utterly enameled in ice and is Incapacitated. If it is dealt Bludgeoning, Thunder, or Force damage, the ice shatters, ending the condition. Gains Vulnerability to Bludgeoning, Damage Types Thunder, and Force damage. Gains Resistance to Fire damage. Gains immunity to Burning and Encrusted with Frost until no longer Frozen.

Item 3 | Necklace of Elemental Augmentation: Enter the Creche. Do what you want but once you get to the Inquisitor and vanquish him, the room to the right (if facing the same direction as when you entered) has said necklace. The benefit is that when one of your Cantrips deals Acid, Cold, Fire, Lightning, or Thunder damage, add your Spellcasting Modifier to the damage dealt. By now this should be a +4 or a +5.

Item 4 | Coldbrim Hat: Whenever you're done with the Mountain Pass and the Underdark, head on to Act 2 through whatever method you prefer. Once in, head directly to Moonrise Towers and act as if you belong. If you follow that Half-Orc lady and talk to her, she'll give you a key to Balthazar's room. Take it and head in, close the door, and check one of the corpses for a heart on the floor. Grab it. Then walk up to the bookcase. There are multiple books that act as levers with most being trapped. Find the one talking about organs and pull it. When you do, a pedestal will open. Add the heart. Another room will open. Inside the chest in that room is the Coldbrim Hat. The benefit of the hat is that whenever you apply any condition to an enemy, they also now gain 2 turns of Encrusted with Frost. Because Encrusted of Frost itself is also a condition that is being added from your Clutches, you are now adding 4 turns of Encrusted with Frost on every successful attack.

Item 5 | Potent Robe: Upon getting the hat, head towards the Prison/Dungeon in the basement of Moonrise. Here there are a number of Tieflings that are held behind bars with some guards patrolling around. Whether through conversation or violence, make sure that you will not be seen and help the Dwarves. I would highly recommend either giving them a hammer or going to get the hammer they require. While you can just open the gate, they'll head through the front door and things will be way more difficult. When they smash open the wall they'll save the Tieflings and escape through a secret passage that leads to a boat. You can go with them if you like or just head to Last Light Inn yourself and meet them there. Inside the main chamber of the Inn is Alfira, the bard. She is reunited with someone close to her and celebrating. Talk to her and she will give you the Potent Robe, the best set of robes any Charisma Caster can ask for. Why? The benefit of the Potent Robe is all of your cantrips now do damage equal to your Charisma modifier and at the start of every turn you will gain temp HP equivalent to your Charisma modifier.

But there's still one more thing to grab.

Item 6 | Snowburst Ring: On the ground floor of the Inn, in the back right (provided you're facing the direction when you came into the building) is a single room with a Tiefling child in it. Upon passing a perception check you will spot some floorboards that are loose. When you remove them you find the ring. The benefit of the ring is that whenever you apply any cold damage, a patch of ice 4.5m/15ft will appear under the enemy and they must make an immediate dexterity saving throw or fall prone.

At this point your Ray of Frost should be getting +15 to all damage thanks to your subclass and various items, provided your Charisma is 20. When the enemy becomes chilled from your staff (or wet from other stuff) they take double damage for a minimum of 32 points of damage with a maximum of 70. You're also getting a pretty decent bonus to your attack rolls so the vast majority are going to hit anyway. Even more so If someone has Faerie Fire. Then you have the Encrusted with Frost that has a low save which means most people are succeeding and then taking even more cold damage which somethings will affect. Because that cold damage is coming from you, it also means other things can apply and because of your hat, anytime something applies so does Encrusted with Frost. You just keep stacking up psychotic amounts of cold damage. Now that's from a single fucking cantrip that outperforms most spells but you're a sorcerer. You can fire three of those, minimum, per turn. Add in haste? 5 attacks per turn.

Congratulations. You're now terrifying. Have fun!