MTG Salvation

6/15/2010 You may target zero, one, or two creatures. The creatures don’t need to be untapped.

6/15/2010 If you target zero creatures, Repel the Darkness can’t be countered for having no legal targets. When it resolves, all that happens is that you draw a card.

6/15/2010 If you target one creature and that target is illegal as Repel the Darkness resolves, the spell doesn’t resolve. You don’t draw a card.

6/15/2010 If you target two creatures and they’re both illegal as Repel the Darkness resolves, the spell doesn’t resolve; you don’t draw a card. If just one is illegal, the spell does resolve; the remaining legal target becomes tapped (if it’s untapped at that time) and you draw a card.