Are these sentences worded in the correcy way?

FYI- Dyrr is the lichdrow. With Lolth again granting spells to her followers, the drow gained the advantage in the siege, and Vhok retreated with his forces, leaving the duergar to be slaughtered by the dark elves. Gromph was aware that he would have to destroy Dyrr’s phylactery to prevent the lichdrow from regenerating, and he began to devise a plan with his fellow Baenre mages.