End Mystic Carrion's Immortality

Thrumbo wishes to escape Mystic Carrion.

Defeat Mystic Carrion is a sub-quest of the quest  Find Mystic Carrion's Servant in Act Three of Baldur's Gate 3. It can be started by speaking with Thrumbo in the Lower City.

Objectives

Investigate Mystic Carrion's mansion.

• We killed Mystic Carrion, but he seems to have resurrected and killed Thrumbo. There must be a way to kill him for good. Maybe his mansion holds answers.
• We killed Mystic Carrion, but he resurrected, and now he's angry. There must be a way to kill him for good. Maybe his mansion holds answers.

Find Mystic Carrion's secret basement.

• We agreed to help Thrumbo permanently defeat Mystic Carrion. He told us to look for a chamber beneath Carrion's mansion.

Explore Mystic Carrion's secret basement.

• We found Mystic Carrion's secret basement. We should look for information about his experiments.

Find Mystic Carrion's Ancient Lair..

• We discovered that Mystic Carrion used to work from an ancient, subterranean crypt. If we find this lair, we're bound to find some of his most well-guarded secrets. We might have luck looking for it somewhere in the sewers.

Explore the Ancient Lair.

• We found the Ancient Lair that Mystic Carrion wrote about. We should look for clues about where his heart might be.

Find Mystic Carrion's heart.

• We found a note in Mystic Carrion's lair and learned that he has been putting jars containing his organs within his zombie servants to preserve his life force. It's clear now where to find Carrion's heart.
• We found one of Mystic Carrion's canopic jars. It's radiating with necromantic energy. It may not be his heart, but destroying it will certainly weaken him.

Tell Thrumbo that Mystic Carrion's heart is inside him.

• We found a note in Mystic Carrion's lair and learned that he has been putting canopic jars containing his organs within his zombie servants to preserve his life force. We must tell Thrumbo.

Destroy Mystic Carrion's heart.

• We killed Mystic Carrion, but he seems to have resurrected and stolen his heart back from us. We must get it back and destroy it to defeat him for good.
• We told Thrumbo that he had Carrion's heart in his chest and he vomited it out. We should destroy it.
• We found Mystic Carrion's heart. We must destroy it if we are to kill him for good.
• We managed to destroy one of Mystic Carrion's canopic jars with fire. We should do the same to the one that contains his heart.

Destroy Carrion's heart

• Mystic Carrion's heart is destroyed. If we kill him now, he will die for good.
• We gave the jar containing Mystic Carrion's heart back to him.

Walkthrough

The location of A Mummy's Memoir.

End Mystic Carrion's Immortality is started after choosing to side with Thrumbo during  Find Mystic Carrion's Servant. To kill Mystic Carrion for good, his heart must be destroyed. Thrumbo mentions he was brought down to a cellar by Mystic Carrion, so the Philgrave's Mansion is a good place to begin searching.

The party must head up to the second floor to find an iron ladder (X:19, Y:-153) leading down to the Mystic Carrion's basement lair. Within the lair is a book called A Mummy's Memories which references an ancient lair in the Undercity Ruins. Alternatively, there is a hole in the wall (X:27, Y:-166) that can be bypassed using  Wild Shape,  Disguise Self,  Gaseous Form, or other means.

Location of Funerary Jar Form and Function.

Then the party must travel through the Lower City Sewers to the Undercity Ruins waypoint, then head west to discover a passageway (X:-180, Y:934). Entering the passageway leads to the Ancient Lair and a room full of gilded chests with varying amounts of gold. Also in the middle of the room in the open sarcophagus is found the Breaching Pikestaff. While in this room the entire party is under the curse Spell Rot (Condition). Opening any chest or lockpicking the door (DC 20) causes a horde of undead monsters to rise up and attack the party. A hidden door on the north wall (X:-1390, Y:75) leads to Mystic Carrion's workshop, with a book called Funerary Jar Form and Function (X:-1395, Y:84). Reading it reveals that Carrion's heart is inside of Thrumbo. The Jar of Mystic Carrion's Brain and Jar of Mystic Carrion's Liver can also be found here.

If returning to Thrumbo and telling him the heart is inside of him he is disturbed and pukes up the Jar of Mystic Carrion's Heart. The jar can be destroyed using ranged attacks, as it explodes on destruction dealing 8d6Fire. If giving Mystic Carrion's Heart back to him, or if he steals it from the party, it can be found again in his basement. Destroying the heart completes the quest and updates  Find Mystic Carrion's Servant with the objective to return to the mansion and face off against Mystic Carrion, to free Thrumbo and his friends once and for all.

Other Jars

Three other canopic jars can be destroyed to weaken Mystic Carrion, but doing so is not necessary to permanently defeat him:

• Jar of Mystic Carrion's Brain is on a table in the Ancient Lair
• Jar of Mystic Carrion's Lungs is in the Graveyard's Mortuary basement
• Jar of Mystic Carrion's Liver is in a Gilded Chest in the Ancient Lair

Quest Rewards

• Crypt Lord Ring - Given by Thrumbo if he was sided with.