Most towers and baileys are defensive, protecting defenders from attackers. This keep tower and bailey is used to protect everyone else from what is within.
Some time magic users are less magical than one expects.
The district gets its name by the good sized walls that are painted a bright blue that mark the magic district. That wall is watched by the Witchhunter guard.
Helioglyph (his magical name) is a Talismonger, a maker of charms, talismans, holy items, and so on. This is the place where those seeking fine craftsmanship and good symbolism come. If you are looking for enchanted items, go elsewhere.
The secret for immortality has been discovered by an eccentric wizard/mad scientist. Its found you need to reapply once a month. As people stop dying, and the birth rate increases exponentially, people are forced into homelessness, because of the need for food reamins the same, and food is not being produced fast enough to feed the undying population. The PCs have to find the creator and kill him, and destroy production, to save the world from undying, unending torture from hungryness.