Weatherlight, Gerrard's Ship

When this creature enters the battlefield,
you may pay {x}{x}. If you do, search your library for X artifact cards with converted
mana cost X or less, and exile them with a
cargo counter on them.
{x}: You may cast target card exiled with a
cargo counter on it. If the amount of mana
you payed is equal to it's mana cost, you can cast it without paying it's mana cost.