I attack the maximum number of remaining skeletons (if there are fewer than three, it doesn't matter which ones).
Skeleton-4 takes 324 - 40% = 194 damage
Skeleton-4 takes (crit) 648 - 40% = 388 damage (-82/500)
Skeleton-5 attacks Illurin
Miss
Skeleton-6 attacks Illurin
Miss
Illurin attacks Skeleton-5
Miss
Miss
Skeleton-5 attacks Illurin
Miss
Skeleton-6 attacks Illurin
Miss
Illurin attacks Skeleton-5
Skeleton-5 takes 324 - 40% = 194 damage
Skeleton-5 takes 324 - 40% = 194 damage (112/500)
Skeleton-5 attacks Illurin
Illurin takes 600 damage (2400/3000)
Skeleton-6 attacks Illurin
Illurin takes 600 damage (1800/3000)
Illurin recovers 600 health
Illurin attacks Skeleton-5
Miss
Skeleton-5 takes 324 - 40% = 194 damage (-82/500)
Skeleton-6 attacks Illurin
Miss
Illurin recovers 600 health
Illurin attacks Skeleton-6
Miss
Skeleton-6 takes 324 - 40% = 194 damage (306/500)
Skeleton-6 attacks Illurin
Miss
Illurin attacks Skeleton-6
Miss
Miss
Skeleton-6 attacks Illurin
Miss
Illurin attacks Skeleton-6
Skeleton-6 takes 324 - 40% = 194 damage (112/500)
Miss
Skeleton-6 attacks Illurin
Miss
Illurin attacks Skeleton-6
Skeleton-6 takes 324 - 40% = 194 damage (-82/500)
Alaria, Tylen, and Silverfall meet Illurin just as she delivers the killing blow to the last of the skeletons.