Board Thread:Theories and Rumors/@comment-31916385-20190227143634/@comment-31916385-20190227143843

The third symbols was above the door from where the ninja came and it looks like Ninjago, so it is most likely Ninjago.

The first one looks like Spinjitzu so it could be connected to the First Spinjitzu Master, maybe the Realm of Oni and Dragon are another realm the he had created.