If you control a Swamp, destroy target nonblack creature.
Splice onto Arcane—Exile four cards from your graveyard. (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)
2/1/2005 Horobi’s Whisper can target a creature even if you don’t control a Swamp, but the spell does nothing.
6/7/2013 You reveal all cards you intend to splice at the same time. Each individual card can be spliced only once onto any one spell.
6/7/2013 A card with a splice ability can’t be spliced onto itself because the spell is on the stack (and not in your hand) when you reveal the cards you want to splice onto it.
6/7/2013 You choose all targets for the spell after revealing cards you want to splice, including any targets required by the text of any of those cards. You may choose a different target for each instance of the word “target” on the resulting spell.
6/7/2013 If all of the spell’s targets are illegal when the spell tries to resolve, it won’t resolve and none of its effects will happen.