He strolls up to one of the entrances of the Black Dome, walking and at a normal walking speed, his acquired Teleport destination having been a couple of miles away in Sothis. He does not particularly wish to make a production about traveling too quickly, through the city, including by flying about invisibly, and he's not wasting multiple Dimension Doors on popping around that way.
"Hello," Ri-Dul says to the fanciest-looking guard there. "I'm told you've acquired a certain Carissa Sevar. I am sent here by my employer, Keltham, to bring her to him."
He looks unmagical and like he doesn't have an alignment aura, unless somebody is looking very hard.