Quest chain about Souleater
Set up next to the Wraithgate portal. It looks like there is some space between the arc of Primeval Towerlings, but this is likely to fail.
Use Souleater item after combat has started. The Vicious Devourer is not always aggressive to Souleater's user (this may also be true of the item that weakened Suzerix), it will not initiate combat when used. Because Vicious Devourer has been damaged, and he has "left combat" as soon as it is used, he immediately begins regaining life, and the item is entirely wasted. Just trash the quest and start again if this happens, but of course, the trick is to use the item after combat has started.
It is not surprising that, with a time limit on it, Souleater is not required to finish the quest. However, it is a little surprising that Huo lets you keep it if the timer has not run out on it yet. It has a value of 1 coin, but cannot be sold.