Digsite Conservator

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.

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.

You exile the cards face up. All players will be able to see them.

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 spell has any mandatory additional costs, you must pay those to cast it.

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.

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