Frost Aura (Bookworm Bwikki)
From Guild Wars 2 Wiki
Frost Aura is an aura that chills foes and reduces damage that Bookworm Bwikki will apply during a guild bounty. Unlike the version applied to players, the aura and the chill it inflicts upon attackers last much longer.“
Chill foes that strike you. Incoming damage is reduced by 10%.
— In-game description