Scholar of the Lost Trove

If you cast a spell “without paying its mana cost,” you can’t choose to cast it for any alternative costs. You can, however, pay additional costs. If the card has any mandatory additional costs, those must be paid to cast the spell.

If a spell has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.

If you wish to cast the target card, you must cast it while the triggered ability is resolving. You can’t cast it later in the turn.

If you cast an artifact spell this way, it won’t be exiled if it would be put into your graveyard this turn.