Link to the Mothership article:
https://magic.wizards.com/en/articles/archive/news/dominaria-leak-2018-03-08
Original Reddit thread:
https://www.reddit.com/r/magicTCG/comments/830v71/chinese_dominaria_faq_possible_leak/
So far the set looks to include Legendary sorceries (which can only be cast when you control a legendary creature or planeswalker), Saga's (which are enchantments that play out like sorceries which are stretched over several turns), and the return of Kicker. Along with the planeswalker damage redirection rules change that was announced recently.