Deep Gem

Deep Gems are upgrade materials in Dark Souls III.

Availability

 * Irithyll of the Boreal Valley - From the Central Irithyll bonfire, head through the elevator that is revealed after opening the nearby shortcut and go down a set of stairs. It can be found between between a Fat Minister and a balcony in the large open room.

Usage
Infuses weapons with Dark damage, increasing base damage as well, although removing all other types of stat scaling.