I'll give this one a go. The Trayus Academy was probably constructed by the ancient Sith Empire, being the Empire who challenged the Republic during the Great Hyperspace War, and abandoned after the war ended. After that is was probably rediscovered during Vitiate's exodus in search of Dromund Kaas and became a part of the new Sith Empire. Between that point and the Mandalorian Wars it was abandoned for a unknown reason.
Wow great stuff, I wish there was more to read about him!
EDIT: I guess my question is about Malcore, when was that Sith temple constructed there? Just like with Dromund Kass I know the Old Sith Empire had a habit of collapsing in on it self a few times and fringe colonies being left to rot and forgotten about.