Arcanic Rune Stone
Arcanic Rune Stone is an Imbuing ingredient needed to imbue the Mage Weapon property onto weapons. It can be found as loot on creatures living in the Cavern of the Discarded.
As of Publish 61, a character with 90 Tinkering and 80 Magery can craft Arcanic Rune Stone by using a tinkering tool along with 1 Crystal Shards and 5 Power Crystals. Look in the Assemblies submenu.