Ruin Raider

• WWizards of the Coast2017-09-29
  Official Ruling
  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.
• WWizards of the Coast2017-09-29
  Official Ruling
  If the revealed card doesn't have a mana cost (because it's a land card, for example), its mana value is 0.
• WWizards of the Coast2017-09-29
  Official Ruling
  If the mana cost of the revealed card includes , X is considered to be 0.
• WWizards of the Coast2024-11-08
  Official Ruling
  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.
• WWizards of the Coast2024-11-08
  Official Ruling
  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.
• WWizards of the Coast2024-11-08
  Official Ruling
  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.

Rulings via Scryfall