I always thought that, given that Luke's spirit appeared in Legacy to get Cade to combat Krayt, and their encounter in Apocalypse that ended on ominous terms("you must not be so certain Master Skywalker"😉 that eventually Luke was going to die at Krayt's hand.
Well that was before Disney and Legends.
The OP should ask Denning if maybe he heard something about that.
I think it makes sense.
If Luke
a) is aware there's another Sith Order running around
b) knows from Jacen's vision that Krayt will eventually sit on the Throne of Balance with Allana at his side
there's no way he wouldn't attempt to do something about it. And with Krayt and the rest of his order still being alive and kicking a century later, Luke obviously had to have failed.
The most logical inference was that Krayt eventually made an overture to Allana and he either corrupted her or forced her into serving him(or a combination, much like he attempted with Cade) and uncle Luke rode to the rescue.
So Krayt and Luke fought, maybe with Wyyrlok and the rest of Krayt's inner circle ganging up on Luke. Luke got killed, probably sacrificing himself in a desperate attempt to save her. Krayt was left a cunthair away from death, just like on Had Abbadon. Allana is in shock and sees the error of her ways but she doesn't pay attention to Krayt, who she thinks is dead. She goes on to lead the Jedi etc.
Krayt is rescued and goes into stasis for a long time. No more activity for the one Sith. The Jedi think they're wiped out. A century later Legacy happens.
You know it's true.