Possession: how evil is this?

[Kae'Yoss]

But the presence of negative energy does not mean there is the presence of evil. If that were true, then Inflict spells would have the Evil descriptor. Enervation would have the Evil descriptor. Undead does not equal evil.

Undead does equal evil. The state of undeath itself is a mockery of life and therefore undeath is evil. It doesn't mean the undead has to be evil, though (and a good Undead will show as good creature with detect good).

Undead does not equal negative energy. Many spells that deal with negative energy are not evil, but simply battle spells (that can be used with an evil purpose): Inflict spells, Harm, and Enervation are means to fight your foe, just like fireball.

I focus less on the "letter" of the law, and more on the "spirit" of it. The spell's intention is to detect evil and that's all it will do IMHO. Others can focus on the loophole provided by strict interpretation of the "letter" of the spell and allow it to do much more.

There is no loophole. Undeath is an evil thing, the spells to create undead are evil, and so the results of these spells are evil, too.

 

[nharwell]

That does seem a good way to handle it Nharwell but what me and the other GMs of our group are trying for is "standard DnD"
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Well, speaking from a strictly "standard DnD", by-the-book approach, Magic Jar is NOT evil as it does not have an evil descriptor -- not in the PHB nor in any of the errata or FAQs. However, I assumed that the question was how other GMs treated it in their games, since the "official" ruling is rather clear....