Cones, Emanations, and Detect Magic. A RAW reading.

[Sparrowhawk_92]

There was a discussion on another forum regarding how to handle the cone of light from a flashlight moving during play and whether it took an action to set the facing of the light during a turn. While we didn't find consensus, I decided to search for precedence elsewhere to help the discussion and I ran across this odd bit of RAW that I wanted to share and get others take on.

The spell Detect Magic creates a cone-shaped emanation with a range of 60 ft, with a duration of concentration with a maximum duration of 1 min/level. However, according to the rules about duration for spells, I came across this fun bit of text.

CRB p 335 wrote:

If the spell affects an area, then the spell stays within that area for its duration

This suggests that once you cast detect magic, it only affects the cone-shaped area that you originally defined during the casting and does not move with the caster.

I decided to check the text on emanations under "defining effects" to see if it offered clarity.

CRB p 268 wrote:

Emanation: An emanation effect functions like a burst, except that the effect continues to radiate from the point of origin for the duration of the effect. Most emanations are cones or spheres.

And the text for defining a cone:

CRB p 268 wrote:

A cone-shaped effect extends away from you in a quarter-circle in the direction you designate. It starts from any corner of your square and grows wider as it goes. Most cones are either bursts or emanations (see above), and thus won’t go around corners.

Does this suggest that the caster is the point of origin and that the cone from detect magic moves with the caster, defining the caster as the "point of origin" for the spell (which I think is the most common de facto practice) or would the corner that you're casting the cone from be considered the point of origin for the spell and therefore the cone effect would not move with the caster (by RAW)?

[BigNorseWolf]

Each round you concentrate on the same area, you can determine if one magic source you detect is from a spell, magic item, or other effect, and the caster level (or item level) of the effect.

Implies you can move it around.

If the spell affects an area

Detect magic has no effect on the area. It's effect is on the caster to let them detect the magic. You can throw detect magics left and right and still get your cleaning deposit back. Cloudkills and fireballs, not so much.

[Darg727]

Because it is an emanation, the point of origin is you as you have surmised. The area is set each round you concentrate. Note, if you stop concentrating the spell ends.

To weigh in on the flash light debate; making it an action you can make at anytime during your turn, except during an action, I think is probably the best way to do it. Flashing a light around takes minimal time irl and using a swift/move/standard is really too much to be practical mechanically. This makes it easy to use, but it doesn't overshadow the lantern for off turn use.