Board Thread:General Discussion/@comment-27252392-20161023022308/@comment-24020008-20161124170343

They already killed off Epsilon, so if Season 15 starts with Donut (who survives death a lot), Sarge, and Tucker missing, they are most likely wounded trying to escape the Staff of Charon, and will come back when they are back to full health.

But Tucker was around for 5 seasons before his disappearance, Siris was around for less than 1. I'd compare it more to Season 9, where in the past we saw new characters (Carolina, the Freelancer CT, and the Innies like Sharkface). At the end of the Season, I could see Siris making an appearance in the present, like how Carolina did in Season 9, but it would have to be explained.

But yeah, hunting down Locus (even though Locus specifically said he won't be seen again (obvious lie by writers)) is a good reason to seek out the Reds and Blues.