When picking cards, you cannot use more than 4 of the same card, with the exception of basic energy cards
It also sees play in some of the more traditional versions, usually as a two-off and in lists with Eternal Witness as they combine well together
Only creatures controlled by a battle's protector can block creatures that are attacking that battle
With specialize you can pay mana and discard a card to change your card to one of five different specializations, according to the color of the card or land that you discarded
Liliana's Mastery is a fast way to punch through your opponent's defenses, and Liliana, Death's Majesty is a must-answer planeswalker
Otherwise, getting new cards to fill out your card dex seems to be a wait-and-see approach