Invoke Lightning

Acquisition
Signet of Capture:
 * Nightfall
 * Lushivahr the Invoker (Yatendi Canyons)
 * General Tirraj (Dzagonur Bastion (mission))
 * Scribe Wensal (Nundu Bay (mission))
 * Tanmahk the Arcane (The Sulfurous Wastes, during A Show of Force)
 * Portal Mage (The Shadow Nexus (mission))
 * Curator Kali (Gate of Madness (mission))
 * Eye of the North
 * Shadow Spawn (Raven's Point)