... The Guild has no idea why you've got the idea that they are part of the Old and Venerable Eleusinian Order, but you might as well register with the guild and take a few jobs while you investigate the invitation.
Use anything from here except for "Setting Specific" things.

AGRIPPINA FENG the Branch Head. The reclusive aasimar manager of the Neverwinter Adventurer's Guild. From the glimpses of her you catch, you see she is pretty human in appearance. The only thing indicative of celestial parentage is the heavenly chanting that fills whatever room she is in.
YAKAU OSIPOV the Information Lead. A half human man who gathers the Branch's rumors and quest listings. He travels often and likes to bring back regional pastries.
V. G. SUN the Quarter Master. An barn owlin with a terrible past as an artificer and armorer during the bloody Owl Civil War. They've since moved out of the Feywild with family and settled in a Neverwinter suburb.
AEGLE the Receptionist. A friendly hologram of a woman who offers membership, quests, and payment.