Things developed more smoothly than Fang Jie had anticipated, because a battle between Legendary Experts could not be completed in just a day or two. Especially when dealing with Fierce Beastmen who possess superior physical strength.
Unless one employs spirit attacks that restrain them, their vitality is simply too exuberant.
A typical Legendary Expert can fight for three days and nights, but these Fierce Beastmen, I fear, can battle for five. Such attrition, even his Skeletons are having a tough time bearing.
Undead Creatures have advantages in all aspects, but they also have disadvantages in all aspects.
Battling it out in terms of endurance with such vigorous creatures is not an advantage of the Undead.
Hence, the hidden Death Knights could only lend a hand. For instance, by using spells to boost their comrades or by providing their allies with some regeneration to help them withstand such a lengthy duration.
