The outpost of Tor's Edge on one of the cubes of Acheron contained a vault where the Mercykillers had hidden a few scrolls of Mnemur. Like the Arcadia Incident, the attackers were reported to be bestial in nature, and had appeared from nowhere. The Mnemur scrolls were stolen.
The following symbol was found drawn in blood on one of the iron walls in the compound:

The investigation is still ongoing.
