Hashmalum
Explorer
Some new assassin spells in the Book of Vile Darkness have the [evil] descriptor. A non-evil character can cast evil spells--he just won't stay non-evil for very long if he does so. The only restriction with regards to casting spells with an alignment descriptor is found in the class abilities section of certain divine spellcasting classes, and the restriction is merely against casting spells that have an alignment descriptor that is opposite to the character's alignment. The limitation only applies to those classes and it is not a general rule.As the assassin learns spells like a wizard and none of these spells has an [evil] descriptor AFAIK, they shouldn't be related to some special alignment.
Killing is not in itself evil. The victim, the circumstances, and the motivation make all the difference. There's nothing inherently evil in the death attack, either--it's simply an extremely precise attack. As such, it's no more evil than the sneak attack.I would agree that a non-evil assassin who wants to stay non-evil can't use his death attack to kill someone and shouldn't use poison.
As for using poison, that isn't evil in itself either--it's merely unchivalrous. As long as the assassin hasn't switched class to paladin or something equally fussy, I don't see the problem.
Becoming more resistant to poison is a function of the body's natural reaction to continued exposure. The more you are exposed to a poison or drug, the higher the tolerance you will build up to it. Consider the example of a chronic morphine addict--their bodies have become so desensitized to morphine that the amount needed to give them a buzz would be enough to kill a normal person.Losing his save bonus to poisons seems to be ok, too (become more resistant to poison is more supernatural or comes from a divine source, IMHO).