If you control a Forest, each blocked creature gets +2/+2 until end of turn.
Splice onto Arcane—An opponent gains 5 life. (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 Roar of Jukai can be cast even if you don’t control a Forest or there are no blocked creatures. If you control no Forests or if there are no blocked creatures, 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.