RC wrote:For the most part this rule isn't one that causes you too much trouble. The only real drawback it has is the "ray of enfeeblement" against blackguards tactic and similar stuff.
Well, when you lose the preqs to a feat, you don't actually lose the feat. You just lose the use of the feat. It is still one of the feats you chose and you do not erase it from your character sheet (like a lost level).
So casting a Str ability damage spell would not cause you to lose the Power Attack feat and the prereqs for Blackguard.
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The prereq text is below.
SRD wrote:Some feats have prerequisites. Your character must have the indicated ability score, class feature, feat, skill, base attack bonus, or other quality designated in order to select or use that feat. A character can gain a feat at the same level at which he or she gains the prerequisite.
A character can’t use a feat if he or she has lost a prerequisite.
I'd say that the "lose the prereqs to a class, lose the abilities" interpretation would make it very hard lose class abilities during the course of a game.
Classes which grant abilities or conditions that mess with its own prereqs are notable exceptions to the rule. They must obviously be exceptions or else the game breaks apart.
However, that seems unnecessary since the SRD uses this text for PrCs:
SRD wrote:Prestige classes offer a new form of multiclassing. Unlike the basic classes, characters must meet Requirements before they can take their first level of a prestige class. The rules for level advancement apply to this system, meaning the first step of advancement is always choosing a class. If a character does not meet the Requirements for a prestige class before that first step, that character cannot take the first level of that prestige class. Taking a prestige class does not incur the experience point penalties normally associated with multiclassing.
Since this is the only PrC text in the SRD, and there is no errata or FAQ ruling to contradict it, one can make the argument that this is the "definitive and final" ruling on PrC rules, which means that PAOing into a Dwarf to become a Dwarven Defender for a level and then going back to being a Elf after the first level is completely kosher.