The Voidseer's Pearl is a bauble added by Thaumcraft 6. It is used to provide a Vis discount directly proportional to how much permanent Warp the player has incurred.
The Primordial Pearl can be at any durability.
— Thaumonomicon, Voidseer's Pearl
When I hold this charm I get glimpses of what lies beyond. The meaning still eludes me, but I feel more connected to the aura and magic than I have ever felt before.
While I have this charm equipped I will find vis much easier to manipulate.
Oddly enough, the size of the bonus seems to be proportional to the amount of permanent warp I have suffered. What a strange coincidence.