The Agility assistant is a fairy that assists players during Balthazar Beauregard's Big Top Bonanza, often referred to simply as the circus. The player can talk to the Agility assistant for an explanation of the Agility performance portion of the D&D. During conversation she will elaborate on juggling, and how to perform the various tricks as a part of the performance.
If the player wishes to end their performance early, they can speak with the Ranged assistant before completing the ten allocated spells in activity.
This article on an NPC has an associated transcript page. Click here for a transcript of possible conversations and other messaging related to this NPC.