Offering of Blood

Acquisition
Signet of Capture:
 * Hormak Ironcurse (Ice Caves of Sorrow (Mission))
 * Jollen Steelblight (Frozen Forest)
 * Morgriff Shadestone (Grenth's Footprint)
 * Riine Windrot (Thunderhead Keep (Mission))
 * Tonfor Copperblood (Lornar's Pass)

Energy gain
This presumes Offering of Blood is cast as often as possible (activation + recharge time) before any activation/recharge time modifiers.

Related skills

 * Energy Boon