Caparocti Sunborn

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 Caparocti Sunborn is untapped as its ability is resolving (for example, if it has vigilance), it can be tapped for its own ability.

You can tap any two untapped artifacts and/or creatures you control, including creatures you haven't controlled continuously since the beginning of your most recent turn, for Caparocti Sunborn's ability.

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

When you discover, you must exile cards. The only optional part of the ability is whether you cast the exiled card or 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.

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.