That is not an eight, it's the symbol for infinity
Assuming you only get back 1 monster, here is the wording based on how I understand it: Once per turn, during your Battle Phase, if your opponent activates a card or effect after an attack is declared: Banish the attacking monster
Since Liliana of the Veil is available in modern, players will never pick a more expensive Liliana, Waker of the Dead, so this one will only see play in standard, pioneer, and commander
When discussing mana in print, the convention is to use letters in order to reflect which symbols we are talking about when we aren't able to just use the symbols
You can obtain the Type: Null (2-Diamonds rarity) card by opening Extradimensional Crisis from Extradimensional Crisis set