[Seska]

Well, my idea why she is there in the crashed Simoun.

Spoiler:

When Angelus suicide, she destroys the Simouns on deck. Perhaps she set the "inner something" of the engines free. And they suck her into "Tempus Spatinum".

*Shruk* or Angelus was already dead, and "Tempus and Spatinum" let her revive in this time and space (dont forget what Onashia says, about the two became a pair).

Or more easly. The Highlands are the orginal Simouns users and crafters. The Simouns that the Corps are flying was digged up of the grounds right? Perhaps thats the half truth.