Whenever Elvish Mariner attacks, scry 1.
Whenever you scry, tap up to X target nonland permanents, where X is the number of cards looked at while scrying this way.
In the days of the Kings, most of the High Elves dwelt with Círdan or in the seaward lands of Lindon.
Elvish Mariner's last ability cares about the number of cards you actually looked at. For example, if you were supposed to scry 3 but only had two cards in your library, X would be 2.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.