If the Wyrm Master has at least one Imp summoned, any attack directed towards the Wyrm Master will instead be redirected to a randomly chosen (and unfortunate) imp. A message will appear for both the attacker and the defending Wyrm Master, alongside the regular attack message.
Area of Effect attacks, as they do not target any single person, are not interposed by the Imps.
Attacks made by pets can also bypass the thrall. Due to random pet targeting and the low HP of imps, all of the imps tend to be killed before the Wyrm Master, unless the Wyrm Master has specifically provoked the attacking pets.