I'm not sure if this is a real issue or just something hidden I can't find. The in-game book reads:

When in a coven, only one member of the coven must ingest this concoction in order to allow their whole coven to access the powers of the demon.

After summoning Baphomet, everything worked correctly, but I am still not clear how to make a coven, and my friends are getting torched quickly.

Thanks for your help!

Covens are not in yet, this was referring to a feature we planned but decided to hold back for 1.16 and may change/not do anyways