Laslo Tremaine said:
H
Player B (a cleric) follows the next round and discovers player A in a frozen/held/paralyzed state, with a Barbed Devil near-by. Player B uses out of character info to know that Player A is under the effect of a "Hold Person" as a spell-like ability cast by the devil, and states that he will use a targeted Dispel Magic to get rid of the Hold effect.
Was it *really* out of character knowledge?
I'm assuming that, as a cleric, your player's character had several ranks in Knowledge (Religion), which, last I checked, covered things like:
SRD said:
Religion (gods and goddesses, mythic history, ecclesiastic tradition, holy symbols, undead)
So, while a Knowledge (The Planes) roll would certainly cover the abilities of various well-known demonkind / devilkind, a Knowledge (Religion) check might also reveal the common abilities of his religion's most hated foes, which might include such creatures: "And the horde of Grim'zk the Undying fell upon the host of Saint Epicalia, and blood did water the ground like a summer rain. Like the wheat of the field, or the sands of the shore, yea, that was the count of those who were slain, held rigid by the devils' unholy magic. And lo, Saint Epicalia held the Talisman of Drussh on high, and spaketh, invoking the Seven Holy Names, and so the magic's grasp upon her holy soldiers was loos'd, and with a righteous cry they fell upon the unholy host."
Something to think about, anyway.
Can you dispel a spell that that you think might be on a target?
I'd allow it, with the knowledge that, if it's not there, you just wasted a Dispel.
EDIT:
Alternatively, if you think that the target is a Dispel Magic cast on a creature, and you target that spell, but the *actual* cause of the paralysis is, say, a Holy or Unholy Word, you've also just wasted a spell.