The tat on May’s head is the same as the symbol on the witches forehead from the trailer, I think her mom’s may have been witches or one of them at least. Sol recognized the symbol and so did Indara. I get the feeling Indara talked the other two or three Jedis into killing May because she sensed the potential for the Sith in her, kind of a Ben Solo situation where the Jedi are so afraid of the Sith that they wouldn’t risk it. Sol may or may not know they tried to kill May and her sister thinks May started the fire that killed their family because she sensed the darkness in May too. That could be why she quit the Jedi,fear of turning to the dark side herself. That’s why Indara didn’t want her trained, fear that she could fall like they saw May possibly doing, they are dyads, two beings whose souls are connected, so like May, her sister is connected to darkness too. The fact that the Jedi tried to kill a child and they found out or more people might find out, would explain why it was erased from the archives. I don’t think May’s master is a master, but an apprentice. We know what Sith were alive in this time period and we’ve seen who she has been meeting with, none of those Sith Lords giant heads are fitting in that little helmet they are wearing, that person is not the master, more likely an apprentice lining up their ducks to kill the master and for May to be their apprentice. Plagueis head is to big and long to be in the helmet, I think we are looking at a Jedi either turning or playing at being a Sith to bring down the order.