Eberron: Shadow of the Mark
A Karrnathi human working in Sharn
The address that Zee has, if it coincides with this Baltasar person, is in Graywall, Tavick’s Landing. Not far from Deathsgate, actually, a neighborhood with a lot of Karrnathi.
Reminder: Baltasar is the person who hired some rogues, including Quarion, to spy on the PCs months ago.