[ Well, of course Wei Wuxian knows the requirements. It's his ritual, after all. So, when he talks about it, it's a little breezily, like none of this matters in the first place and they're talking about the weather. ]

Eh, it's nothing too complicated. It's called "Sacrifice" since the person who performs it has to sacrifice themselves to the spirit they call. They give up their body and their life and in exchange, the spirit has to adhere to their last wishes or they'll be destroyed, never to reincarnate. It's kind of a last ditch thing, no one's that desperate to use it. Usually.

[ Unless you're Mo Xuanyu.

Then there's a pause and he remembers who he's talking to, immediately narrowing his eyes at Xue Yang. ]

For the record, you can't force someone to do it for you either. It's a contract between a spirit and the sacrifice. A third party getting involved would mess it all up.