<Snipped quote by TheTwistedOne>
A blood ritual doesn't always have to result in death, I have seen where just the spillage of blood and whatever other rituals is enough.
Once on some show, the blood ritual used just the amount that came out from a pin prick.
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.