Siphon

Extremely old

Used as a means of transferring extremely powerful... raw magical powers.

Several of these were placed strategically throughout the world's crust at these various nexus points as a means of creating extremely powerful relics, like some of the vestiges.
But most are inert or lost
Siphons guaranteed have two points that are connected by the siphon
Unclear if these points need to be on the same plane or not.
NPCs theorize that whatever is put in is crushed and separated in to it's purest components, but they can't be certain since no device or spell that would allow them to observe such a journey survives the trip.

Theories

Possible that these Siphons use planar mechanics in order to function, so potentially the efficiency of them goes up dramatically during Winter's Crest, where the barriers between the planes are thinner. This COULD explain why Delilah Briarwood was so concerned about moving up the time table on the ritual, she knew it probably wouldn't work, or would potentially exact a much higher cost.

Also, very interesting that Siphons are referenced as being involved in the creation of some of The Vestiges of Divergence. The vestiges were mostly linked to the gods so far, but there are some like Whisper that aren't explicitly linked to gods in their known lore. It could be that the big sin that the dark gods committed during the Age of Arcanum was teaching mortals how to create The Vestiges of Divergence (or at least artifacts on the same power scale as a god-created vestige). This feels even more right with Whisper specifically, given that it's described as being at the center of "many a dark ritual".

Item type

Magical