XP from opponents created using PC rules

If the PCs defeat, say a 4th level Mage, should they be awarded XP as if it had been a regular 4 HD monster?
Or should there be extra for special abilities?

Page 149 has a list of special abilities worth extra xp. Spell casting is definitely on it. I’d also say that magic item use ought to be on there, and probably make a difference between low and high level spells (because being able to throw a magic missile is nowhere near as dangerous as a fireball).

I think the reincarnation rules count spell casting as ** and since special ability XP scale with HD a simple ** would work. I wouldn’t add XP for magical items because they are their own prize when defeating their owner.

i asked in another thread some time ago about sticking a class to a monster (Monsters with classes). alex said, that non-spellcasting classes would add one asterisk, while spellcasting classes would add two.
yesterday a re-read some of BECMI’s maste set rules and found, that one asterisk is added per two spell levels a creature can cast.
there are two possibilities to determine XP gained by defeating classes: with your example of the 4th level human mage:

  1. to become a 4th level mage you would need 10.000 xp, so you earn 10.000 xp if defeating one.
  2. (if i have it right according to aforementioned thread) a 4th level mage is a human would be 4* (being able to cast 1st and 2nd level spells) and thus would garner 80 (base XP) + 55 (1 asterisk XP) = 135 XP.
  3. is way too much, so i would stick with 2)

The official rule is that they count as a number of HD equal to their level, plus one special ability for divine casting and two special abilities for arcane casting. You can, of course, modify this as appropriate for any particular NPC.