Reweave | Magic: The Gathering
Formats Reweave is Legal in
Official Oracle Text for Reweave
Splice onto Arcane (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.)
Official Rulings for Reweave
11/1/2005 : The player reveals cards only if the targeted permanent gets sacrificed.
4/1/2008 : With the introduction of the Tribal type it became possible for an instant or sorcery card to share a type with the sacrificed permanent (ie, a Tribal instant card shares a type with a Tribal Enchantment card). Reweave has received errata so that the effect looks for a *permanent* card that shares a type with the sacrificed permanent. A permanent card is a card that could be put onto the battlefield, which is any card that isn't an instant or sorcery.
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 will be countered and none of its effects will happen.