pf2e.fyi
From Pathfinder Treasure Vault (Remastered), which isn't enabled.

Whisperer of Souls

ITEM 28
UNIQUEARTIFACTDEADLY-D8DIVINEFORCEFULREACH
Usage held in 2 hands
Bulk 2
Category martial
Group polearm
Damage 1d8 slashing

This +4 major striking greater brilliant keen glaive binds the souls of powerful creatures it slays. The soul can't be returned to life by any means while imprisoned within the glaive and can be freed only by a deed of great benevolence or selflessness. While using the glaive as a weapon, whenever you reduce a sapient creature of 18th level or higher to 0 Hit Points or roll a critical success with a Strike against such a target, the creature must attempt a DC 50 Fortitude save.

Critical Success No additional effect.

Success The glaive siphons the creature's essence, rendering it Drained 1. If the creature dies from the Strike or while drained in this way, the creature's soul is bound in the glaive.

Failure As success, but the creature is Drained 2.

Critical Failure As success, but the creature is Drained 4.

The glaive also has the following activations.

Activate (concentrate)
Trigger You Strike with the Whisperer of Souls
Effect You choose whether the Strike deals lethal or nonlethal damage. If the glaive has a reason for doing so, such as slaying a creature whose soul the glaive can absorb, it can defy your choice if you fail a DC 50 Will save.
Activate (concentrate)
Trigger You attempt an Occultism check to Decipher Writing, Identify Magic, Learn a Spell, or Recall Knowledge
Effect You listen to eldritch secrets the weapon whispers, gaining a +4 item bonus to the triggering check.
Activate (concentrate, manipulate)
Frequency once per week
Effect Attempt an Occultism check as if you cast the Collective Memories ritual about a subject. If you roll a success or critical success, you can repeat what the Whisperer of Souls relates to you about the subject. On a critical failure, you and the glaive are drawn into a murmuring void of cold, where your mind is assaulted by strange visions for an entire week. At the end of this time, you reappear and must attempt a DC 50 Will save.

Success When you return, you can retrain one of your skills into a Lore skill about evil creatures or places, as if you had spent 1 week retraining.

Failure As success, but you are Stupefied 2 for 1 week.

Critical Failure As success, but your alignment moves one step toward evil and you must retrain one of your skills into a Lore about evil creatures or places. You become obsessed with increasing your forbidden knowledge, turning to wicked forces that offer such secrets and compromising your morals further if you must.

Destruction If the Whisperer of Souls is used to slay Shelyn's herald, it disintegrates, bringing about great evil in its wake.

Pathfinder Treasure Vault (Remastered)ORC