The main characters really can't catch a break, huh.
First it's the Beast of Apocalypse, supposedly able to destroy the continent and stronger than gods or dragons, who was neatly dealt with following a competently executed plan, followed by a sudden maximum power duel with the battle junkie Arsoon who ends up becoming some kind of temporary(?) ally and now it's an ancient vampire king AND Arsoon's elder sister dragon?
Insanely rushed pacing for this final arc, but I guess it's to be expected given this ending.
It's over. Abruptly. Not a very conclusive "ending" at that.
Oh well, off the the Completed pile with you.