Choose any target. Scry 3, then reveal the top card of your library. Riddle of Lightning deals damage equal to that card's mana value to that permanent or player.
2021-03-19
If a card in a player's library has {X} in its mana cost, X is considered to be 0.
2021-03-19
If the chosen target is an illegal target by the time Riddle of Lightning tries to resolve, the spell doesn't resolve. You don't scry 3 or reveal any card.