Question The Sister Spell

A blood binding is more in the nature of invoking the Laws of Magick (and of magickal beings) than it is a matter of Essence/power or even spell casting. As such... it is both more powerful and more inherently 'wild' than practical spellcasting.

The reason it is such a big deal for Fey and Carmilla is because they are both beings whose nature (and blood) is inherently the stuff of magick... a baseline mage could quite literally draw essence out of their blood (if it weren't for the fact that Fey's blood is protected by ancient Sidhe Court magick to deteriorate almost immediately after being taken from her body).

So for Nikki and Sara to exchange blood is in itself an act of magick. On top of that they swear an oath binding them (a Sorceror's contract under the Law of Solomon). Any actual spell casting atop that is almost overkill really...

So, could any two or three regular mutant Wiz's do the same? No.

But could they do something similar? Sure. Sorceror's Contracts would still be at the foundation of any sworn oath between them. The Laws of Magick would still apply. More of the power would have to either come from the casters OR would come in the nature of 'wild' magick. Personally, I'd want to feed the spell myself, because when you start allowing yourself to be bound/enforced by wild magick... strange things happen.