Xeltan is usually found next to Ambassador Calyn in the Embassies. When Commander Shepard meets him, Xeltan doesn't want to talk. He is there on business to complain about the asari Consort, Sha'ira. He says she has compromised his authority but refuses to go into details.
After speaking to Septimus on behalf of Sha'ira, Shepard learns that Sha'ira is innocent: Septimus revealed one of Xeltan's secrets, and blamed Sha'ira. Shepard gives Xeltan evidence proving Sha'ira wasn't involved. Xeltan is shocked. He knows Septimus and claims he couldn't have discovered his secret, but the evidence is irrefutable. Xeltan becomes worried that if Septimus could find out, anyone could. Shepard can assure him that it would be extremely hard for anyone else to discover the secret, or let him sweat, and Xeltan goes to speak to Sha'ira.