The mana value of a split card, such as cards with aftermath from the Amonkhet block, is based on the combined mana cost of its two halves.

If the revealed card doesn't have a mana cost (because it's a land card, for example), its mana value is 0.

If the mana cost of the revealed card includes , X is considered to be 0.

Some raid abilities trigger at the beginning of your end step. These abilities trigger if you attacked with a creature that turn, even if the permanent with that raid ability wasn't on the battlefield when you attacked.

Raid abilities care only that you attacked with a creature. It doesn't matter how many creatures you attacked with or which player, planeswalker, or battle those creatures attacked.

Raid abilities evaluate the entire turn to see if you attacked with a creature. That creature doesn't have to still be on the battlefield. Similarly, the player, planeswalker, or battle it attacked doesn't have to still be in the game or on the battlefield.