Signet of Capture

Use Signet of Capture on a boss who has just used a skill you want to learn. Signet of Capture is permanently replaced by that skill. (You can only learn skills of your profession.)

Where To Get It
Magi Magister in Lion's Arch gives you a quest with this skill as a reward. Thereafter, you can purchase additional signets from him or any other Skill Trainer NPC. Alternatively you can purchase it regardless of completed quests at the skill trainer in Quarrel Falls.

Usage
Using a Signet of Capture is the only way to learn Elite Skills, though regular skills can be captured as well. Signet of Capture must be bought from a skill trainer. This signet can only be used on bosses, and you can only capture skills of your primary or secondary profession.

To capture an elite skill from a boss begin a fight with that boss, and upon killing it cast signet of catpure. This will list all the skills that were available to this boss and you can pick a skill to capture. Once a skill is captured, Signet of Capture is replaced by the captured skill until the next time you enter an outpost or city. A new Signet of Capture must be purchased to capture further skills.

Historic Usage
Before the update on 8th June 2005 Signet of Capture captured the last skill used by the boss, provided you had not already learned it.