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I recently played with a mob that could cast deeper darkness at will. Up until now the spell seemed very clear to me, because I just considered that there was basically a sphere of 60 feet around the object on which it was cast, where the effects of the spell were applied.

However, the following line in darkness's description is a bit puzzling to me:

If darkness is cast on a small object that is then placed inside or under a lightproof covering, the spell’s effect is blocked until the covering is removed.

This line basically introduces the fact that the spell does have interactions with its environment.

This got me wondering what happens if a mage just cast the spell at the bottom of a town's wall. Would the spherical area of the spell just go right through and make the other side of the wall darker (making the bag thingy an exception to the spell's function)? Or would that not work, and the wall would block the spell? Would the height of the wall make any difference (if the wall was higher than the spell's radius for example)?

I am guessing that RAW, the spell would just go through (although I would still like a confirmation about that), but I am also interested in what you people would rule it.

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  • \$\begingroup\$ This question is a more specific version of this question Not that there's anything wrong with that. \$\endgroup\$ – Hey I Can Chan Jun 2 at 6:27
  • \$\begingroup\$ Closely related, although not duplicate (different system). \$\endgroup\$ – annoying imp Jun 3 at 19:26
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When the darkness spell description says, "If darkness is cast on a small object that is then placed inside or under a lightproof covering, the spell’s effect is blocked until the covering is removed," it's explaining to the reader how the rules deal with the fact that this isn't an ordinary area spell.

Ordinarily, a spell that has an Area entry radiates outward from a point of origin, a grid intersection (or, if you prefer, a crosshairs) that was picked by the caster when the spell came into effect. (See also Aiming a Spell on Area.) In addition to cluttering the battle mat, that point of origin also determines how—or even if!—the spell's area extends past any obstacles in the area.

However, unlike normal area spells, the subject of the spells darkness et al. are objects, and those spells' areas radiate from the objects that were their targets. That makes these spells' areas more sensitive to interaction because they're usually small and mobile. For example, while a 10-ft. cube of butter (or whatever obstacle you prefer) can be dropped onto a point of origin to squelch an ongoing area spell—making it so every angle from the spell's point of origin is occluded by an obstacle—, it's far easier for a sneaky halfling arcane trickster to cover with his hand a coin on which he's cast the darkness spell. Even though creatures aren't usually obstacles enough to interfere with a spell's area, covering the coin, were told by the darkness spell's description, nullifies the darkness spell's area until the trickster uncovers the coin.

So the description of the darkness spell is here adding rules that, in an extremely rare display, we might go so far as to call as common sense: A dude can put in his belt pouch a rock on which has been cast the darkness spell and, even if the GM would've normally ruled that a belt pouch is an insufficient obstacle to block a spell's area—which the GM normally should—, here, because of that explicit text in the darkness spell description, that belt pouch blocks the darkness spell effect.


  • Question: What if a caster picked as the target of the darkness spell the bottom of a wall?

    Answer: Because the question asks specifically how folks would rule on this, here's how this GM would rule: He wouldn't let a caster pick that target. Nobody really liked my answer as to why I wouldn't allow it, but I don't care: Allowing it makes my brain hurt with all the cascading gamewide implications. That is, the spell says, "This spell causes an object to radiate darkness," so if in your campaigns you want glowing houses or shadowy houses, then go ahead and allow structures or parts of structures to count as objects. In my campaigns, I just don't allow such spells to target structures or, for that matter, individual parts of things (e.g. a foe's mouth, one tile of a tile floor).

  • Q: Okay, but if the GM were to allow a caster to target a wall with the darkness spell anyway…?

  • A: It's possible the entire structure radiates darkness—the wall and everything it's attached to shedding darkness to the limit of the spell's area. Alternatively, that lone brick that the caster picked that's part of the wall sheds darkness, and if that brick is the same brick on the wall's opposite side, then there will be darkness there, too, albeit occluded by any bricks above or below. (Unlike a spell with an effect entry, the caster doesn't need to see the entirety of an area spell for the spell to come into effect successfully.) However, if you don't like either of those options, though, then you'll have to make up something.

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  • \$\begingroup\$ I had in mind that the caster would drop a little rock at the bottom of the wall more than he would cast it directly on the wall, sorry that i was unclear about that \$\endgroup\$ – Lymakk Jun 3 at 16:52
  • \$\begingroup\$ @Lymakk No problem! Should I address that possibility in this answer, or is what happens in that regard already clear enough here? \$\endgroup\$ – Hey I Can Chan Jun 3 at 16:55
  • \$\begingroup\$ As I understand, it would basically travel around the wall, thus reaching the other side only if the wall is shorter than 30ft \$\endgroup\$ – Lymakk Jun 3 at 17:12
  • \$\begingroup\$ @Lymakk Around to a degree, I guess, but still not through. Imagine the rock shedding light instead of darkness and what would happen were the rock put next to the wall. The game's saying that the same thing that would happen in real life with that glowing rock would happen in the game with that darkness-shedding rock. Does that make sense? \$\endgroup\$ – Hey I Can Chan Jun 3 at 17:20
  • \$\begingroup\$ Yeah it does, thank for this clear answer, i was mainly put of by the wording of the spell ^^ \$\endgroup\$ – Lymakk Jun 4 at 19:26
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Because the example of darkness being blocked being analogous to the way light from a lantern would be blocked, the implication appears to be that the magical darkness works the same way as light.

It reaches every point within the radius that has line of sight to the point of origin.

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