[quote=@Odin]
<Snipped quote by Burning Kitty>

I mean, summoning an ancient god that has been locked up for x amount of time would probably require a bit more than that, but I get the gist of what you're saying. :lol
[/quote]

A human can lose a pint before death becomes a problem. Now one could start removing blood and saving it. Then you can get all the blood you need for the ritual without killing someone.