The Ancient Lair is a secluded part of the Undercity Ruins. It is accessible only from the Lower City Sewers via a short side corridor starting just west of the Undercity Ruins waypoint. At the end of the corridor at X: -180 Y: 935 is a passageway which leads into a separate location.
While exploring the Lower City, the party can encounter Mystic Carrion - a mysterious entity providing various esoteric services for the wealthy citizen of Baldur's Gate. Delving deeper into the issue, they can find out that Mystic Carrion is a mummy lord who spent ages in his subterranean crypt, but left it deliberately as he needed to replenish his stock of alchemical ingredients and experience what the surface world has to offer.[1]
If the party wish to successfully confront Mystic Carrion, exploring the Ancient Lair is a necessary part of the End Mystic Carrion's Immortality quest. The lair consists of a grand tomb with a small antechamber, and an attached workshop.
The antechamber is empty save for the corpses of three adventurers, who seem to have found the lair and tried to loot it (a fourth such corpse is in the workshop). None of them respond to Speak with Dead.
At X: -1368 Y: 63 is a tombstone propped against the wall. The inscription on it reads "Those who draw breath, embrace death". Reading it prompts a comment from the Narrator.[2] This formula provides a clear hint on how to explore the tomb in a safer way.
The grand tomb is a vast cavern with a stone platform in the centre, surrounded by four stone pillars. The north-western pillar is destroyed, with only the socle left, which can be climbed upon. In the centre of the platform is an empty stone sarcophagus with the Breaching Pikestaff inside.
At X: -1389 Y: 72 a DC 10 PerceptionCheck highlights a locked wall section, which can be lockpicked with DC 20 Sleight of HandCheck to open. Behind it is Mystic Carrion's workshop (see below).
The grand tomb is filled with Opulent Chests and Gilded Chests in plain sight. Additionally, a pile of Treasure Crates lies on the ground near the hidden wall. Several chests lie destroyed, though no loot is scattered around them. None of the chests are locked or trapped. They contain various sums of gold, from several dozens to several hundred. The treasure pile may have a random precious gem; the chest in the westernmost corner holds some alchemical ingredients as well.
Several corpses of mummies and zombies, as well as multiple severed hands lie scattered around the cave. Opening any of the chests, looting any of the undead, or opening the door to the workshop triggers an ambush, resurrecting all creatures and making them hostile to the party. At the same time, the door leading back to the antechamber closes and locks by itself, requiring DC 20 Sleight of HandCheck to lockpick. Despite the obvious suddenness, the party do not receive the Surprised condition and can fight at once.
Additionally, living party members are inflicted with the Spell Rot curse. Spell rot causes each character to take 2d6Necrotic damage per spell level every time they cast any spell requiring a Spell Slot. Cantrips and the Clerics'Turn Undead ability do not trigger the curse's backlash.
While the curse can be temporarily removed, it is re-applied after three combat rounds. It is lifted upon leaving the lair. Also, characters who climb on the broken pillar in the north-western corner do not suffer from the curse as long as they stay atop the slab. If one or several party members are left in the antechamber when the undead rise and the door closes, they still suffer the curse. However, there are exceptions to this.
If a fight starts, it is advisable to prioritize Ancient Servants, as the combination of their attacks and actions, Dreadful Glare and Rotting Fist, makes them the most dangerous opponents in the room. Also, as the Crawling Claws have only 4 HP (5 HP on Tactician difficulty), it can be useful to eliminate them one by one under the Elixir of Bloodlust, easily gaining an additional action.
The locked movable wall section leads to a small workshop. On the table is a chopped up body with the Jar of Mystic Carrion's Brain among the gore lumps. Any party member may comment on the sight. On the floor behind the table lies a dead half-elf. He can be communed with using Speak with Dead.
Several broken cupboards in the side alcoves may contain a minor amount of gold.
A ladder to the north of the workshop leads into a small chamber with a lever at X: -155 Y: 949. Pulling it opens another movable wall right behind Bareki's back, allowing the party to return to the Undercity Ruins. This room cannot be opened from outside.
Opening this exit from the Ancient Lair provides an opportunity to quietly loot Sarin's Skull from a red-outlined pouch guarded by Bareki.
The canopic jars found in the lair can be destroyed to deprive Mystic Carrion of several buffs which help him in a fight (see his page). Only his heart found in Thrumbo must be destroyed to prevent Mystic Carrion resurrecting after a long rest. However, destroying any of the jars causes a large explosion dealing 8d6Fire damage (which can be useful, as the jars are vulnerable to fire damage). Therefore, it is recommended to gather as many jars as possible[3] and place them close together to destroy them simultaneously with a single ranged attack, far from any objects and NPCs to avoid collateral damage.
Astarion can avoid the fight with the undead horde in the Ancient Lair. The whole horde-resurrecting trap is designed to not trigger if the lair's master (i.e., Mystic Carrion) – a powerful undead creature – is moving about. Thus, Astarion, being an undead himself, can either interact with any lootable object or attempt to open the hidden wall in the grand tomb chamber. Doing so either results in a passive DC 20 WisdomSaving Throw, rolled for each interaction. On a successful roll Astarion is able to loot a chest or enter the workshop without disturbing the undead guards. Astarion is unaffected by the Spell Rot curse as well.
If a party member romances Astarion and agrees to become his spawn after he ascends, they, by extension, gain the same benefits (including the Saving Throws option) attributed to their new undead nature.
↑ The game files provide a set of comments from various companions as well, but as of game ver. 4.1.17209685 none of these pop up. The corresponding file is LOW_PhilgravesMansion_PAD_AncientLairTablet_001.
↑ There are four jars total. The fourth jar, storing Carrion's lungs, can be found in the Mortuary cellar of the city graveyard. Picking up the first jar (whichever) in a playthrough prompts a comment from the interacting party member about the necrotic energy emitting from it.
