The amount of Magical Essence consumed when transferring an individual was related to that individual's strength.
Ashu transferred ten Demon soldiers of varying power consecutively, and from this he concluded that sending a Demon to the human world required consuming Magical Essence equal to five percent of the Demon's own Magical Essence.
Now, in "Reaper's Resolve" mode, Ashu's power level was at mid-Grand Archmage. Even transferring those four patrol members from the inner circle was no problem, let alone ordinary Demon soldiers.
The only issue was the sheer number of Demons—he couldn't transfer them all at once. And great Demon Shava's strength was especially formidable; five percent of her Magical Essence was probably equivalent to eighty or ninety percent, if not a full hundred percent, of Ashu's own.
In "Reaper's Resolve" mode, Death power was exclusive; other skills were unusable.