Thank you, some more questions.
Even the pit fiends summoning? and its invisibility scaling?
they say:
"
Invisibility:as a SLA 1/day for each HD. At 6 HD See Invisibility, Invisibility Purge and other such anti-invisibility effects except True Seeing don't bypass the Pit Fiend's invisibility unless the observer is whitin 10 feet. At 14 HD not even True Seeing bypasses it unless the observer is whitin 10 feet of the creature/object subject to Invisibility.
"
and
"
Summon Devil:Twice per day as a standard action, the Pit fiend can summon reinforcments, depending on its HD:
3HD:2 lemures
5 HD: 4 lemures
8HD:2 bearded devils or 8 lemures
10HD: 1 Erinyes or 4 bearded devils or 16 lemures
12HD:2 Bone Devils or 2 erinyes or 8 bearded devils or 32 lemures
14HD: 1 Ice Devil, or three bone devils, or three erinyes, or 16 bearded devils or 64 lemures.
18HD: 1 Horned Devil, or two ice devils, or eight bone devils, or eight erinyes, or 32 bearded devils, or 128 lemures.
20HD: two horned devils, or four Ice Devils, or sixteen Bone Devils, or Sixteen Erinyes, or 64 Bearded Devils, or 256 Lemures.
"
How about the entries refering to levels? Take the Ak'Chazar Rakshasas spellcasting? It says:
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At 2nd level the Rakshasa, Ak'Chazar becomes able to cast as a sorcerer of 4/5 his level (thus advancing this casting at every level but 6th and 11th, for a total of 12th level sorcerer casting at 15th level).
"
I assume that it refers to levels in the Ak'Chazar Rakshasa class and not character level.
In other words, the spellcasting progression is tied to the class progression and not the the characters level progression.