If you're lucky, you can get a sacrifice scene (i.e. priest and sacrifice and altar). Most of the time, you might get better results if you just go for the altar and/or the priest. A lying person on an altar seems to be very difficult.

It's not where I would like it to be, but let's see what different checkpoints can do ... so pictures please.

My "Dark Ritual" LoRA is more about ... dark rituals (summoning something) ... this here is more about sacrifice but there are no clear lines. Maybe one gives you better results than the other?

Edit: sacrifice (body) on altar is possible with quite a bit of img2img and inpaint ...