So, whoever is more knowledgeable about magic, do I need a teacher for blood magic or can I give a character small access to it without magical background? Or know a form of magic from a teacher and experiment from there?
I do not entirely get how or why it can't be used in game if it is accepted lore and we have other forms of powerful magic. Was it just to OP for players to RP with?
No. If you look on the thread, Connor asks if players could refrain from using the magic. I presume it'll be open in 4.0, but I'm not 100% sure. I'd also imagine you'd need a teacher, so speak to the creator of said magic.