Given how RS time travel seems to function much like Whovian time travel (you can change some things, but others will happen no matter what), I'm expecting Aeternam to function somewhat like Riversong in that they tend to live backwards when compared to the standard flow of time (the time period of our past is their future, and the time period of our future is their past).
Alternatively, they could be the one actually responsible for why certain events in RS are 'fixed.' Essentially, they'd dip in and out of the time line altering events in order to encourage certain outcomes.
12-Jan-2017 12:33:11