User blog comment:Alemon97/DEATH BATTLE! Season 2 Retrospective/@comment-5035900-20170401003820

The thing with Night Terror is that it's... well...

It only appeared in just one game, Soul Calibur III... and even then, the form never actually appeared in the canon story, as Soul Calibur IV stated Siegfried and Nightmare fought at the end of III, but with no Night Terror.

As for Night Terror's power, it's entirely pure speculation. Is Night Terror all-powerful because of the dimension you fight him in? Even giving him the benefit of the doubt, Nightmare at most could destroy a castle or wipe out an army of surrounding soldiers. Now I don't do scaling, but even with that, there's nothing there to support Nightmare jumping from that to "planet" potential as Night Terror.

Honestly, with it's virtually non-canon status, I think Night Terror was just thrown in to make viewers potentially feel like Guts could be in trouble.