SRD Talk:Magic Missile
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3.5e magic missile, the wording is vague, can it work only in less then total concealment, indicating the writers were lazy in not clarifying what looks like a clear exception of the following
"Some spells have a target or targets. You cast these spells on creatures or objects, as defined by the spell. You must have line of sight to or be able to touch the target, and you must specifically choose that target. You don’t have to select your target until you finish casting the spell. You must have line of effect to any target that you cast a spell on." 3.0 rules compendium.
In 4th You do not need Line of Sight unless the spell specifies it (Rules Compendium pg. 106). Magic Missile does not have this restriction.
so with all the information presented it is rather vague, however as it seems to me at least "The missile strikes unerringly, even if the target is in melee combat or has less than total cover or total concealment. = "The missile strikes unerringly, even if the target is in melee combat." And/or "The missile strikes unerringly, even if the target less than total cover." And/or "The missile strikes unerringly, even if the target has total concealment."
in complete (deeeper) darkness the wording would be in my opinion, if the creature is in combat then the dc to hear him is 0, if you succeed by more then 20 then you pinpoint the square the enemy is in and may now target the creature within (seemingly if the creature is sharing the square perhaps the DM can then chose the target since you were either unaware their was 2 targets or split the damage between them)