Portal was a ruined city located on Onyx Island in 3437 P.X.E.. Portal was home to Edmund, the last Guardian of Onyx Island, who refered to the city as his. It was apparently a frequent resort for Silver the Hedgehog, as well as the apparent home of Mammoth Mogul. Prominent features of the city include a library containing fragmentary records of Mobius' past, as well as a large statue of Lara-Su. (SU: #25)
- Although the city was shown in earlier issues, it wasn't until Sonic Universe Issue 25 that it was revealed to be called Portal when Silver states that the ruined city in the alternate future that he visits looks like the city, Portal, on Onyx Island.