Usually such a process does involve sacrifices of the physical, mental, soul, or other natures. I have checked for hundreds of years for every scrap of information I could find and,

[she puts a hand over her face as she sighs heavily. Her neutral tone shifts to something exasperated.]

this 'ritual' only costs spiritual energy and the blood of the caster. There is no series of carefully orchestrated events. No body count. Nothing like that at all. Just spiritual energy focused through ten souls, and sent outwards, reviving them and then the rest.

We don't even break the chains holding our powers at bay. We're revived right back into the cages that are snuffing our senses and blinding our eyes. 'Shit is whack yo.'. [She drags her hand down and shakes her head.]

The rest is moving the energy, which anyone with spiritual power could do but perhaps the fact a Goddess will be doing said revivals is why the cost is negated. Zange will never give me a straight answer on that.

Of course if they murder her we'll still be sodas with straws sticking out of us. So it might all be moot speculation.