Wrap in Flames deals 1 damage to each of up to three target creatures. Those creatures can't block this turn.
6/15/2010 You may target zero, one, two, or three creatures.
6/15/2010 The “can’t block” effect applies to each of the targeted creatures — and only those creatures — even if Wrap in Flames deals no damage to one or more of them (due to a prevention effect, for example) or Wrap in Flames deals damage to a different creature (due to a redirection effect).
6/15/2010 If any of the targeted creatures is an illegal target by the time Wrap in Flames resolves, it won’t be dealt damage and will be able to block. The other targeted creatures will still be affected.