The Irish-themed pub is a Way Station, a neutral ground for members of both Light and Dark clans; and the place where non-local, traveling Fae in the territory check-in. It also serves as the setting for La Shoshain celebrations.
In The Dal, Fae do not have to hide who they really are.
While The Dal appears to be a normal bar on the upper level, Trick lives within a large chamber in the basement where he has a few things hidden away.
The area beneath the tavern contains a library of information with ancient Fae books that not even The Ash and The Morrigan are aware of; a vault for rare and precious artifacts; a tunnel system used to transport Fae and to escape through; and cells in a lower level (to restrain; and to kennel Under Fae, such as a Satyr).
(Seen or mentioned throughout the series.)