Hidden Cataract

Some spells and abilities that cause you to discover may require targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won't resolve and you won't discover.

If you can't cast the discovered card (perhaps because there are no legal targets for the spell), you'll put it into your hand.

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

A spell's mana value is determined only by its mana cost. Ignore any alternative costs, additional costs, cost increases, or cost reductions.

If you discover an adventurer card, split card, or modal double-faced card, you might be able to cast that card with either set of characteristics depending on the effect's discover value. For example, if you discover 4 and reveal Galvanic Giant (an adventurer card from Wilds of Eldraine with a mana value of 4), you could cast Galvanic Giant, but not Storm Reading (its Adventure, which has a mana value of 7). If you discover 7 and reveal Galvanic Giant, you could cast either Galvanic Giant or Storm Reading.