Speak to Sergeant Geret Dalshinn ( 412, -12, -16 ) /waypoint 412, -12, -16 near the Castle in North Qeynos, or to Elrinn Darknor ( -94, -8, -98 ) /waypoint -94, -8, -98 in North Freeport.
A binding rune, from the Vengeful Seal-Watcher in Dartain's Fortress (Defenders of the Seal side), around ( 661, 126, -221 ) /waypoint 661, 126, -221. Clear some fallen warlocks to spawn it (8-10 up usually. If you kill them all and it doesn't spawn, wait a while for respawn (or go kill another named) and kill some more, and it will pop).