Advancing Monster and CL for SLAs

[Yogibear41]

Looking for the rules on advancing a monster and its CL for its SLAs. In alot of cases it would seems a monsters CL=its HD for its SLAs but in some cases that is not true. Looking at once monster for example that has 6hd, but has a caster level of 12th. Automatically increasing its CL by 2 every time it gains a HD doesn't feel like its the correct scaling either, as that could become ridiculous rather quickly. A quick glance at the MM and the improving monsters section and I don't see the answer. Should the CL stay the same even if the monster advances HD?


Another related question: Familiars with SLAs that have Caster levels. Do the caster levels increase as the Familiars master gains hit dice?

[Troacctid]

Caster level defaults to your hit dice if none is given. If an SLA says it has a particular CL that isn't based on HD or whatever, you can consider that to be a fixed value that will not change if you advance the monster. Of course, you could always increase the CL if you want—you're the DM after all, you can change anything you like, nothing stopping you, yeah?

[Thurbane]

RAW, no, monster SLAs only scale with HD if the monster description specifically says so (Duergar, for instance, or templates like Half-Fiend). In most cases CL for SLAs are static.