Outsider racial hit die progression.

[Jergmo]

Is it generally assumed that Outsiders will prefer to progress by their racial hit die, or does it not matter whether they go by class levels?

[RTGoodman]

Each monster entry states the "usual" way an Outsider advances. Azers (http://www.d20srd.org/srd/monsters/azer.htm), for instance, advance "By character class," meaning they advance by taking levels in a PC class rather than having more Racial HD. The same is true for Aasimar and Tieflings, Rakshasas, and probably a few others.

Most, though, tend to advance by RHD. Their advancement line reads (like this one from the Solar stat block): "23-33 HD (Large); 34-66 HD (Huge)." That's not to say they CAN'T advance by character class (the Hound Archon Hero is an example; normal Hound Archons have HD-based advancement, while the Hero just has 11 Paladin levels), but that you're more likely to find them with just more RHD.

[Jergmo]

Each monster entry states the "usual" way an Outsider advances. Azers (http://www.d20srd.org/srd/monsters/azer.htm), for instance, advance "By character class," meaning they advance by taking levels in a PC class rather than having more Racial HD. The same is true for Aasimar and Tieflings, Rakshasas, and probably a few others.

Most, though, tend to advance by RHD. Their advancement line reads (like this one from the Solar stat block): "23-33 HD (Large); 34-66 HD (Huge)." That's not to say they CAN'T advance by character class (the Hound Archon Hero is an example; normal Hound Archons have HD-based advancement, while the Hero just has 11 Paladin levels), but that you're more likely to find them with just more RHD.

Gotcha, thanks.