The Sillius High-speed fighter is the fighter model utilized by the Hell Hounds mercenary group.
Two Sillius fighters are encountered in Chapter 3 where the Hell Hounds are introduced. They do not prove a problem until all 5 Hell Hounds pilots are introduced by Chapter 4. However, even then, the Hell Hounds manufactured fighters cannot compare to the Emblem Frames. By the middle of the game, Noa gifts them with the superior fighter models, the Dark Angels.