Double Dragon

Acquisition
Signet of Capture:
 * Factions
 * Lian, Dragon's Petal (Wajjun Bazaar)
 * Lale the Vindictive (The Undercity, during Chasing Zenmai)
 * Nightfall
 * The Fury (The Foundry of Failed Creations)

Trivia

 * This skill's name may be a reference to the video game series of the same name.