Arcane/divine and special abilities

[Empirate]

So why can't Warlocks take up divine PrCs to progress their invocations?

 

[Jhaelen]

So why can't Warlocks take up divine PrCs to progress their invocations?

Who says they can't? They can take any prestige classes that advance typeless caster levels. This includes several prestige classes with a divine flavour.

IIRC, there's also one or more prestige classes in Complete Mage specifically created for Warlocks interested in dabbling in the divine.

 

[Empirate]

There's exactly one divine Warlock PrC (Eldritch Disciple), and that advances invocations and divine spells separately.

Sure you can take up "+1 level of existing spellcasting class" PrCs. Even if they have some divine flavor, those classes aren't what I consider divine spellcasting classes.

You can't take up "+1 level of existing divine spellcasting class" PrCs (to progress invocations, that is), only "+1 level of existing arcane spellcasting class" ones. That's what I mean: Warlock SLAs are considered arcane, as far as I can see.

 

[frankthedm]

The default assumption is that abilities based on spells are based on the sor/wiz version. In that case, is the SLA or Su somehow considered "arcane"? If an SLA is based on a clerics-only spell, is it considered "divine"? Is this distinction at all meaningful by RAW?

Very Meaningful since it what IMHO makes the Magebane property Broken.

"...or against creatures with the ability to use arcane spell-like abilities..."

spell Like Abilities
Some spell-like abilities duplicate spells that work differently when cast by characters of different classes. A monster’s spell-like abilities are presumed to be the sorcerer/wizard versions. If the spell in question is not a sorcerer/wizard spell, then default to cleric, druid, bard, paladin, and ranger, in that order.