When Goblin Engineer enters, you may search your library for an artifact card, put it into your graveyard, then shuffle. , , Sacrifice an artifact: Return target artifact card with mana value 3 or less from your graveyard to the battlefield.
Because targets are chosen for activated abilities before costs (such as "Sacrifice an artifact") are paid, Goblin Engineer's second ability can't target the artifact that will be sacrificed to pay its cost.
19-03-2021
wotc
If a card in a player's graveyard has {X} in its mana cost, X is considered to be 0.
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.