Soul Sapper Ring
Gain a little bit of energy every time you slay a monster.
Overview
The Soul Sapper Ring is a ring found in chests in the Volcano Dungeon. While equipped, it restores 4 Energy whenever a monster is defeated, making it useful for sustained combat and long dungeon runs.
A second Soul Sapper Ring can be worn at the same time, and its effect stacks, granting an additional 4 Energy per monster kill. This makes dual-wielding the ring especially effective for players who spend a lot of time fighting in the mines, Skull Cavern, or the Volcano Dungeon.
The ring can also be used in dyeing as a green dye item at the dye pots in 
Official description
Gain a little bit of energy every time you slay a monster.