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, such as kicker costs. If the card has any mandatory additional costs, those must be paid to cast the spell.

Clue is an artifact type. Even though it appears on some cards with other permanent types, it's never a creature type, a land type, or anything but an artifact type.

If an effect refers to a Clue, it means any Clue artifact, not just a Clue artifact token. For example, you can sacrifice Wrench to pay for Alquist Proft, Master Sleuth's activated ability.

You choose whether to cast spells from opponents' graveyards as Jetsam resolves. If you do, you do so as part of the resolution of Jetsam. You can't wait to cast them later in the turn. Timing restrictions based on the cards' types are ignored.

Some spells and abilities that investigate may require targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won't resolve. You won't create any Clue tokens.

A split card's characteristics are a combination of its two halves while it is not on the stack. For example, Cease // Desist has a mana value of 8 while it is in your library. If an effect allows you to search your library for a card with mana value 4 or less, you can't find Cease // Desist.

Each split card has two names. If an effect instructs you to choose a card name, you may choose one of those names, but not both.

Each split card is a single card. For example, if you discard a split card, you've discarded one card, not two. If an effect counts the number of instant and sorcery cards in your graveyard, Cease // Desist counts once, not twice.

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

You can't sacrifice a Clue to pay multiple costs. For example, you can't sacrifice a Clue token to activate its own ability and also to activate Alquist Proft, Master Sleuth's ability.

Split cards have two card faces on a single card. The characteristics of the half you didn't cast are ignored while the spell is on the stack.

Some abilities trigger "whenever you sacrifice a Clue". Those abilities trigger whenever you sacrifice a Clue for any reason, not just to activate a Clue's activated ability.

If an effect allows you to cast a spell with certain characteristics, consider only the characteristics of the half you're casting. For example, if an effect allows you to cast an instant or sorcery spell with mana value 2 or less from among cards in your graveyard, you could cast Cease this way, but not Desist.

To cast a split card, choose one of its halves to cast. There's no way to cast both halves of any of the split cards featured in this set.