Irresistible Blow

Acquisition
Skill quests
 * Prophecies
 * Securing the Vale (Yak's Bend)

Skill trainers
 * Prophecies
 * Firstwatch Sergio (Lion's Arch)
 * Dakk (Ember Light Camp)
 * Factions
 * Masaharu (Seitung Harbor)
 * Nightfall
 * Baram (The Kodash Bazaar)

Hero skill trainers
 * Eye of the North
 * Gedrel of Ascalon (Eye of the North)
 * Kodan (Gunnar's Hold)
 * Tyr the Skaald (Gunnar's Hold)
 * Lexx (Rata Sum)