Power Block

Acquisition
Signet of Capture:
 * Lyssa's Cursed (Perdition Rock)

Usage Notes

 * In PvP play, many characters are entirely focused around a single attribute. Disabling a Monk's Healing Prayers attribute for 13 seconds offers more than enough time for any competent team to finish the job.
 * In PvE play, all bosses in the game (and all foes for that matter) are one single profession, which increases the odds that they mainly use skills from a single attribute, which again gives Power Block a time to shine. However, this skill is less useful in this type of play than in PvP because foes seldom live long enough or are powerful enough to deserve simply disabling their skills.
 * In all cases, try to use Arcane Conundrum or Dazed to make it much easier to interrupt.
 * Power Block will prevent a spell from resolving, even through the protection of Mantra of Resolve or Glyph of Concentration, even though it can't "interrupt"; the secondary effect of denying skills from the attribute will disable the skill being cast, much like a Blackout.

Related Skills
Ranger
 * Distracting Shot
 * Savage Shot

Warrior
 * Disrupting Chop

Necromancer
 * Spinal Shivers
 * Mark of Subversion