In Baldur's Gate 3 Act 3, there are numerous powerful bosses with a mix of very distinctive tactics and vulnerabilities. A general overview is described below for each one:

Viconia DeVir

Viconia is the leader of the Shar cult, the goddess of darkness, and secrets.

Tactics

Viconia employs dark magic and the ability to summon allies.

Avoid darkness: It is an area covered with a lot of shadows which increases her abilities.

Kill her minions fast: Her summoned creatures can get dangerous, so focus on taking them out.

Use light magic: Spells such as "Daylight" could disperse the darkness and also reduce her.

TIPS

Avoid fighting in dark areas.

Focus your firepower on Viconia herself, not her minions.

Keep your characters healthy since Viconia can use some very powerful ranged attacks.

Gortash

Gortash is one of the masterminds of the Steel Watch and possesses very strong fighting skills.

Tactics

Destroy or immobilize the Steel Watchers if one intends to fight Gortash.

Use offensive spells: Spells that damage mechanical enemies or lightning-infused weapons are effective against him.

Tips

Destroy or disable the Steel Watch before battle.

Use lightning spells or other elements against him.

Watch out for traps and his mechanical allies.

Orin the Red

Orin is one of the Bhaal Death Order, expert in close-combat weapons and shapeshifting.

Tactics

Orin can assume the form of your allies, so keep an eye on her movements.

Focus on strong characters: She often targets the strongest members of your party; use support and protection for your tanks.

Increase accuracy in attacks: Orin moves a lot so you need to increase your accuracy on attacks and also make use of crowd control spells to minimize her movements.

Tips

Use support to cover your tanks.

Focus on controlling her movement with spells and traps.

Identify when she transforms into your allies.

Steel Watch Titan

The Steel Watch Titan is a massive mechanism designed to defend the city and its interests.

Tactics

The Titan has a lot of health and strong ranged attacks.

Lightning and fire magic: They are potent against mechanical enemies.

Destroy minor Steel Watchers: Before facing the Titan, it is recommended to destroy or cripple the minor Steel Watchers so that the danger would be minimized.

Tips

Use lightning and fire spells.

Destroy smaller Steel Watchers before the battle.

Be cautious of its long-range attacks.

Lorroakan

Lorroakan is a powerful wizard and an important character in Baldur's Gate 3. He runs a secretive magic tower and is particularly interested in the Netherese artifact, which is tied to shadow magic.

Tactic

Lorroakan makes illusions around him to distract and confuse the player so he should remain careful and try to determine the trick happening behind his back in time.

Tips

Use spells to eliminate illusions.

Concentrate on blasting away his defenders and magical traps.

Keep an eye on the battlefield at all times so that you don't get caught in his illusionary traps.

Ansur

Ansur possesses fire and lightning attacks, which also makes her a dragon:.

Tactics

Fire and lightning resistance: Protection against these elements will be very useful in helping avoid significant damage.

Use ranged weapons: Attack from a safe distance to reduce the dangers of powerful close-range strikes.

Tips

Protect your characters from fire and lightning.

Use ranged attacks in order to counter Ansur's powerful close-quarter attacks.

Keep monitoring his movements and area of effect so you can avoid his massive attacks.

Sarevok

Sarevok is a warrior, the Bhaal servant who possesses superior abilities of fighting with strong stamina.

Tactics

Control magic: Cast spells that restrain him or weaken his battle capabilities.

Avoid close combat: If possible, avoid close combat with him because Sarevok can use devastating melee attacks.

Tips

Use spells which reduce his attack power.

Make sure your characters are well-positioned to avoid his heavy blows.

Auntie Ethel

Earlier in the game, she is Auntie Ethel, but comes with her magical faculties in Act 3.

Tactics

Illusions and traps: Break all her illusions within a short period of time, and be aware of traps. Use dispel magic spells.

Tips

Focus on undermining her illusions and techniques.

Concentrate your attacks on Ethel herself, ignoring all her illusory allies.

Be careful of her manipulations.

Cazador

Cazador is also a powerful necromancer, the leader of the vampires and, of course, a key figure in Astarion's quest.

Tactics

Anti-undead magic: Throw effective spells against the undead against his summoned minions.

Focus on Cazador: Though he can call an army of the dead, focus on Cazador himself.

Tips

Use anti-undead magic to command his army.

Avoid areas where Cazador can use blood magic. Focus on the main boss, but do not forget to manage his summoned allies.

Raphael Raphael 

Is one of the extreme demons with lots of magical power. He has control over the players for most of the game but happens to be one of the toughest opponents at the end.

Tactics

Demonic spells: Raphael can cast powerful demonic spells and summon minions. Take them out to make the battle easier.

Crowd control: Use spells which limit his moves to decrease pressure on your team.

Tips

Eradicate the demonic forces associated with Raphael to reduce the menace. Use fire and magic protection against his attacks. Crowd control spells will keep him under control. The following tips will allow you to be better prepared and have the upper hand when fighting against one of the bosses Baldur's Gate 3 holds in store for you in Act 3.