Dominaria: mechanics

Dominaria mechanics:

• Sagas - is a new enchantment type. As saga enters the battlefield and as your first main phase begins add lore counter and do corresponding effect. Sacriface it when you collect three counters. Adding a lore counter doesn't use the stack. If you find a way to remove a lore counter from a Saga, that doesn't cause any of its abilities to trigger. It triggers only when you put a counter. In this case, you will get the same effect for a second time when you will put a lore counter in your next first main phase. On the other hand, if you put simultaneously two counters, you get two effects.
• Legendary Sorcery - you may cast this spell only if you control a legendary creature or planeswalker. There are no other restrictions on legendary sorceries, so you can cast more than one with the same name in a turn.
• Hexproof from ... - for instance hexproof from black means that this creature can't be the target of any black spells or black abilites an opponent controls.
• Kicker - allows a player to pay an extra cost for a bonus effect. Kicker costs can be paid a maximum of one time
• Historic - sagas, artifacts and legendaries are historic. For instance, when you cast a historic spell you get a bonus effect. 

Legendary cards will have a new frame. Take a look at Urza's Ruinous Blast.