Of all the abilities that the Primordial Ouroboros Serpent contained, this one was one of the strangest for it depended on harvesting outside sources of strength to fuel their own.
That was where the Spirits they collected came into effect, and the Ouroboros Serpents could burn these Spirits, boosting their already formidable Spirit Capacity to a higher degree, with the nature of the serpent, the burning Spirit would not be destroyed, instead it would be sustained by the impossible amount of essence contained by the Primordial Ouroboros Serpents, creating a vicious circle, where the Serpents could burn more Spirits to fuel their abilities, but ensure the Spirits did not dissipate easily.
Converting Essence to heal the Spirit they were consuming was incredibly wasteful, a vast amount of Essence was needed just to heal a fraction of the damages that was incurred by burning the Spirit of their prey, but if there was one thing that the Serpents did not lack, it was Essence.