Take this information with a grain of salt for now, but the folks over at Stitch Kingdom have posted an Ant-Man and the Wasp cast list, and in it, Fringe actor Michael Cerveris is listed as playing Elihas Starr.
September, on Fringe, Cerveris’ other notable roles include Marvin Frey on Treme, James Castro on The Good Wife, Ramses IV on The Tick and Professor Pyg on Gotham.
In addition to playing The Observer, a.k.a.
After being fired for espionage, he turned to a life of crime, only to be defeated time and time again by Ant-Man.