Kregora (20,000 sp): An extremely rare, golden alloy, Kregora
is by far the most powerful of the anti-Essence materials.
Even powerful magical items are temporarily rendered
dormant when surrounded by a Kregora-lined receptacle.
Kregora’s damping qualities are equally effective against all
realms of Essænce (i.e., Essence, Mentalism and
Channeling). Unlike Eog, Kregora will sap a spell user’s
Power Points, the rate of drain corresponding to the amount
of Kregora. Fortunately for spell users, Kregora is rare beyond
description and costly (almost) beyond price.
In 1st edition master atlas, pure kregora had a dispelling effect at levl 500.
You can download all the info from the vault, Shadow World Master Atlas IV appendix B.