When one stores a corpse in a spatial ring, the decay of the corpse would be slowed down, but some spatial rings had the formations and arrays that could slow down the decay of a corpse to a ridiculous level.
The Sword Daemon's spatial ring was one, and it was one of the reasons why when Simon used Devour on it, he sensed that all the things he could devour in a fresh corpse were still available in the Alpha's corpse.
Simon could not just use Devour on any corpse he sees because the longer a corpse dies, the more of the things he could devour would be gone.
However, this was also dependent on the heart rank/power of the demon.
The more powerful the demon, the longer it takes for the attributes in the corpse to dissipate.
The fact that the Sword Daemon's spatial ring could preserve the corpse of the Three-Tailed Alpha Shadow Wolf like it was still a fresh corpse was something that greatly pleased him.
