Candrian Illborne is a planewalker resting in the Smoldering Corpse Bar. He has traveled widely throughout the planes, and is thus a great source of information on many things. He knows much about the portals around Sigil, since they are his primary means of transportation.
Quests
Negative Token
Asking Candrian about the planes – the Negative Material plane in particular – rewards the Negative Token, which acts as a ring and can be helpful in fights against shadows.
Ingress
Candrian can help Ingress find the portal leading back to her home world (750 XP upon returning to him).