Metal Driver

Killing Blows increase Reload Speed by 10% for 15 seconds. Stacks 3x.
Find in the secret passage in the Vault of the Formless dungeon on Losomn.
Lore
The ring's function is surprisingly simple. It does not actually detect when a target is killed, but it detects changes in the wearer's biological state—the excitement of a kill, essentially—and it injects chemicals designed to maintain and enhance that state.
"Although the Drzyr as a people value all life, the Phetyr distrusted created life in any form—particularly the Custodian.
I wish I could say their distrust had been misplaced."