How to challenge PC with arcane eye & arcane sight

[DreadArchon]

First: SRD Vision says nothing about 'MageVision'... you are extrapolating that idea from the text about the casters eyes glowing blue.

Deliberately.

Second... you contradict yourself. If you can't Detect Magic through it... Arcane Eye text reads "The effect is similar to that of a detect magic spell...." and ..."allows you to see magical auras within 120 feet of you." ... or put into your method of phrasing "...going from your head to 120 feet away from it."

Definition 1. Especially look at the American Heritage Dictionary entry (the second in the list).

Arcane Sight
Divination
Level: Sor/Wiz 3
Components: V, S
Casting Time: 1 standard action
Range: Personal
Target: You
Duration: 1 min./level (D)

Detect Magic
Divination
Level: Brd 0, Clr 0, Drd 0, Sor/Wiz 0
Components: V, S
Casting Time: 1 standard action
Range: 60 ft.
Area: Cone-shaped emanation
Duration: Concentration, up to 1 min./level (D)
Saving Throw: None
Spell Resistance: No

Emphasis mine. Arcane Sight is not "going from your head to 120 feet away from it," it's giving you a special vision type ("arcane sight"). "Magevision" is not an actual vision type, but Arcane Sight functions as though it is--indeed, that's why the spell is named like a vision type rather than like a scanning device (and why Detect Magic sounds more like a scanning device than a vision mode). This isn't terribly logical or intuitive, especially by "realism" arguments (given the mechanical functionality of sight), but it is how it's written.

In another attempt at anology, one might say that Detect Magic works like infrared goggles (which artificially translate infrared waves to visible light waves) whereas Arcane Sight simply lets you actually see infrared. Detect Magic detects auras; Arcane Sight makes you detect auras. There is a difference. (That's one of the reasons that Detect Magic is on the same level as "it takes six seconds longer for you to bleed to death" but Arcane Sight is on the same level as "you can raze a city block with your mind.")

taking "It sees exactly as you would see if you were there" to all the nasty possibilities that it can lead to.

I don't see why that *wouldn't* happen, even without allowing Arcane Sight.

This is just another example of poor standardization between editors. The spells could be written much clearer.

Certainly.