Why use Detect Scrying when Scrying counters itself better?

[Kitunenotsume]

As previously considered here, I have noticed that there appears to be no purpose to the spell Detect Scrying, as it (apparently) is less reliable to use than much more common and versatile alternatives.

The spells [Scrying] and [Greater Scrying] have a built in counter, permitting any observer to passively detect the sensor if it is nearby and trace it to the owner to initiate PVP. This is done by a spellcraft check VS a DC between 14 and perhaps 30. This can be performed by anyone who can see invisible things and does so automatically once the sensor is close enough to the detecting character. As a success on this check or on the Will-Save the Scrying spell also permits returns the scrying sensor to the caster, this is an incentive against scrying into whisper range.

Regardless of the saving throws, if a creature in close proximity is able to see the sensor it performs a spellcraft check against the spell's DC to identify the caster. If succesfull, both parties are informed and the eavesdropping party will have auto-consented to PvP. Due to its magical nature, a scrying sensor cannot be seen with Blind Sight.

However, with all this function, another spell intended to counter Scrying exists:
[Detect Scrying] is a 4th level spell explicitly dedicated to countering scrying, but does so in a way objectively worse than how Scrying counters itself. Detect Scrying permits that the Scrying character gets to make a will save VS spells first, which, while not as gameable as a Spellcraft skill DC, can still be quite firmly in competition with spell DCs. This is then followed by exactly the same Spellcraft DC to identify the caster, introducing a significant point of failure into the steps native to the Scrying spell.

When a scrying attempt is detected the scrying entity must immediately roll a will savingthrow vs spells. If this is failed the identity of the scryer immediately becomes known to the caster, derived from the target's magical mark on the scrying sensor. The saving throw is d20 + the caster's spellcraft skill vs the spell save DC of the scryer.

Given that Detect Scrying is a 4th level spell, and lasts for 1 minute per level, it may be compared to the lower level alternative See Invisibility or higher level True Sight - both of which permit more reliable detection of the sensor, and have vastly greater use than only locating scrying attempts.
The argument that it can be made into a UMD device for non-casting character is invalidated simply because the spellcraft check still needs to occur, and the caster of Scrying still needs to fail a spell saving throw. And, as noted, would be better as a wand or potion of True Seeing or See Invisibility for a much greater dungeon utility.

I therefore have a twofold question -
Firstly, why does Detect Scrying exist given that Scrying innately counters itself more reliably?
Secondly, given that Detect Scrying exists, why should Scrying counter itself (given that it does not permit such backtracking in the base spells)?

Thoughts and commentary appreciated.
Cheers,
Kit

[zhazz]

The implemenation of the Scrying spells and Detect Scrying here on BGTSCC are wonky at best, and grossly incorrect at worst.

The logic behind detecting a scrying attempt with the BGTSCC implementation fall into categories:

1. See Invisibility
For someone to detect that they are being scryed they need to be in close proximity to the scrying sensor. Just having the ability to see through invisibility isn't enough. They have to be physically close enough to study the scrying sensor. Consider it similar to reasing a book. Cannot do that from afar.

2. Detect Scrying
Detect Scrying will reveal any scrying sensors within 25 feet, rather than merely at close proximity. Detect Scrying also only uses a single contested roll to determine if the scryer is identified. What is stated on the wiki looks like a copy/paste error (which is quite common everywhere on the wiki).


Here's how Scrying and Greater Scrying function according to PnP rules.

You can see and hear some creature, which may be at any distance. If the subject succeeds on a Will save, the scrying attempt simply fails. The difficulty of the
save depends on how well you know the subject and what sort of physical connection (if any) you have to that creature. Furthermore, if the subject is on
another plane, it gets a +5 bonus on its Will save.

If the save fails, you can see (but not hear) the subject and the subject’s immediate surroundings (approximately 10 feet in all directions of the subject). If the subject moves, the sensor follows at a speed of up to 150 feet.

As with all divination (scrying) spells, the sensor has your full visual acuity, including any magical effects. In addition, the following spells have a 5% chance per
caster level of operating through the sensor: detect chaos, detect evil, detect good, detect law, detect magic, and message.

If the save succeeds, you can’t attempt to scry on that subject again for at least 24 hours.

This spell functions like scrying, except it lasts 1 hour per caster level rather than 1 minute. Additionally, all of the following spells function reliably through the
sensor: detect chaos, detect evil, detect good, detect law, detect magic, message, read magic, and tongues.

You immediately become aware of any attempt to observe you by means of a divination (scrying) spell or effect. The spell’s area radiates from you and moves as you move. You know the location of every magical sensor within the spell’s area.
If the scrying attempt originates within the area, you also know its location; otherwise, you and the scrier immediately make opposed caster level checks (1d20 +caster level). If you at least match the scrier’s result, you get a visual image of the scrier and an accurate sense of his or her

As you can see there is no way in PnP to detect scrying without using the actual spell to do so. As to why the ability to see through invisibility was added as an option here on BGTSCC I can't say. It's plain wrong that it does.


TL;DR
Detect Scrying should only use a single roll, which is made with a 1d20 bonus to detecting the scryer, whereas detection through other means confers no such bonus. That the wiki states two rolls for Detect Scrying is either a typo, a poorly explained mechanic, or a grossly incorrect implementation. Regardless the entire scrying detection mechanic is incorrect in terms of the PnP mechanics.

[Kitunenotsume]

In my experimentation (which is hardly precise), it appears that the Scrying Sensor already tests Will automatically at about half Darkvision radius (and Spellcraft if they have any form of See Invisibility active at the same range). This is likely because in-game spell distances for "Close" or "Short" distance (link) is defined as 25 ft (8m). Therefore my general conclusion has been that Detect Scrying offers no tangible improvement to range.

Secondly, It is my understanding that the entire wonky implementation of scrying counter is because Scrying itself does not follow P&P rules: namely, it creates a sensor closer to [Arcane Eye] (link) might (complete with invisible sensor, movement, and practical distance imitations due to Areas). By P&P, Scrying always targets a person on the same plane (but any distance) who has to fail a Will save, and observes the 10 ft around them. As such, the Scrying countermeasures have been adjusted.

To your point regarding the Wiki, the Wiki has the same text as the in-game spells.

[Antras89]

tbh, more usefull detect scry its on pnp version, when you have chance to see who is scrying you, or location