A Demon Talon is a magic item that replaces a lost arm by grafting itself onto where an arm used to be, and it consists of, basically, a demon's arm. Since it is a magic item with a magic aura, it can be dispelled; the questions remaining are really when/in what state and in what capacity?
Can it only be dispelled before being grafted onto a body, meaning the magic on the item is specifically for the graft, or can it be dispelled AFTER the graft has taken place as well? I think the crafting requirements of Limited Wish and Regenerate would likely suggest the former, meaning that the item just counts as a part of the recipient's body afterward.
Also, what happens when it IS dispelled? I would assume that if it was dispelled while unattached, the arm would just die and become useless (unless something else happens to a fiend's severed body parts that I'm unaware of, like vanishing back to its home plane, or hopping around as a disembodied limb). If it can, indeed, be dispelled once attached, would it fall off, or would it just go limp (and if it did fall off, would the person be bleeding as from a wound, or would the wound be closed already? Would it only fall off if hit with Mage's Disjunction?)?
Of course, not only would all this be important to know in case a character's Demon Talon is targeted by a Dispel Magic, but also for how it would function in an anti-magic field.
It can be used before and after. Dispel only suppresses the magical properties for 1d4 rounds.
If the object that you target is a magic item, you make a dispel check against the item's caster level (DC = 11 + the item's caster level). If you succeed, all the item's magical properties are suppressed for 1d4 rounds, after which the item recovers its magical properties. A suppressed item becomes nonmagical for the duration of the effect. An interdimensional opening (such as a bag of holding) is temporarily closed. A magic item's physical properties are unchanged: A suppressed magic sword is still a sword (a masterwork sword, in fact). Artifacts and deities are unaffected by mortal magic such as this.
Unattached: Unable to be attached for 1d4 rounds.
Attached: Goes limp and loses all power for 1d4 rounds.
So it does still count as a slotless magic item rather than a part of the body, then? Is there any rule to support that, or just lack thereof (meaning we assume it does unless stated otherwise)?