From Guild Wars Wiki
A minion becomes masterless when:
- The character that controlled the minion dies or, in the case of a player character, leaves the instance (e.g. via Log Out or map travel).
- Verata's Aura ends on a character that is in control of minions.
- Verata's Gaze is used on a hostile minion.
- In PvP, masterless minions are shown as gray dots on the compass and their names are shown in gray text.
- Master Architect Gunther uses Gunther's Gaze to kill masterless minions within his earshot.
- A useful tactic is to kill minion masters, which strips your opponents of allies and presents them with additional foes.
- In Fort Aspenwood, the Kurzicks can use this against Luxons who commonly bring minion masters.
- In PvE, this distracts the opponent AI from attacking your own party. Similarly, be prepared to protect your own minion masters, to prevent your own heroes and henchmen from becoming distracted themselves.