Cry of Frustration

Acquisition
Skill Trainers who will teach this skill before it is unlocked:
 * Prophecies
 * Ephaz (Beetletun)
 * Master Scout Kiera (Henge of Denravi)
 * Dakk (Ember Light Camp)
 * Factions
 * Masaharu (Seitung Harbor)
 * Michiko (Kaineng Center)
 * Zytka (House zu Heltzer)

Usage
Because this interrupts all skills and not just spells (as opposed to Power Spike, Power Block, Power Leak, and Power Drain), it is an extremely useful skill to keep equipped, as it is one of the only ways for a Mesmer to stop something such as a Troll Unguent or Resurrection Signet from going off. However, for Mesmers concerned with doing damage and not merely disrupting foes, Power Spike may be a better choice due to the far superior recharge time and damage output.

Because this skill takes a somewhat longer time to recharge, it is imperative to use it very economically, like interrupting a warrior's Healing Signet when they're grasping for hit points. It is also useful to bring support skills such as Mantra of Recovery, Arcane Echo, or Echo to help increase its usage. Alternately, Diversion is also a great help, as Cry of Frustration does not stop an enemy from reusing their skill very quickly, almost always before Cry of Frustration recharges.

Also, one very important aspect of this spell to keep in mind is that it will damage and interrupt all foes (which means their attacks will be interrupted as well, not only skills) in the immediate vicinity, but only if you succeed in interrupting the target foe. For this reason, it is sometimes advisable to cast this skill on the enemy Elementalist or Ranger to ensure that you hit in the middle of a skill with a long cast time, so as to increase your chances of doing the widespread damage and interrupt.