Mirror Of Loss Walkthrough in BG3: Check, Options & Shadowheart

Accessing the Mirror: The Mirror of Loss requires one of two conditions to be met: successfully passing an Arcana and Religion check (DC 25 each), or Shadowheart being a Dark Justiciar (which lowers the checks to DC 20).

Skill Checks: To improve your chances on the Arcana and Religion checks, equip the Warped Headband of Intellect and use Guidance. Having proficiency in Arcana or Religion also helps. Failing a check means you only receive negative effects.

Dark Justiciar Shadowheart: If Shadowheart killed Nightsong, she will likely be a Dark Justiciar. This reduces the skill check DC to 20. Success grants a special message indicating you've sacrificed enough.

Offering Memories: After attempting a check (successful or not), you can offer a part of yourself to the mirror. Each option corresponds to an ability score (Strength, Dexterity, Constitution, Intelligence, Wisdom, Charisma) in that order. Choose the ability score your build needs least, as sacrificing a memory will result in a -2 penalty to that score.

Receiving Rewards: If you passed the initial checks, you can receive a reward. These rewards also correspond to ability scores (Str, Dex, Con, Int, Wis, Cha) and grant a +2 bonus to the chosen score.

Necromancy of Thay Interaction: Characters who have read the Necromancy of Thay can choose to give up their knowledge of the book. This may result in losing the Speak to Undead spell and the Summon Ghouls ability, but it is optional.

Removing Penalties: The -2 penalty from offering a memory can be removed by casting Remove Curse. Clerics have this spell built-in, and scrolls can be purchased from vendors like Sorcerer's Sundries.

Selunite Cleric Interaction: The mirror has a special interaction with Selunite Clerics, attempting to purge their Selunite memories, though it is unsuccessful.