Is the CL of a Faerie Dragon's spells and Greater Invisibility based on HD?

[fearforesta]

While looking at the Faerie Dragon, as I plan on using one as a familiar, I noticed that its HD and its CL for its spells and Greater Invisibility are the same (3).

Is this a coincidence? I already know that the Faerie Dragon's Breath Weapon does scale with its HD, so why not its CL?

[LazarX]

That is correct. in many cases but not all CL for monster sla's ad spells will pair up with HD. The exceptions will be statted out in the descriptions.

Faerie dragon familiars, though if you're asking don't progress beyond that caster level as they do not acquire real hit dice, just 'virtual hit dice" to reflect HD attack tables, the inherited skill ranks, and the inherited saving throw bonues from their master.

[Odraude]

As an addition to this question, what is the Caster Level of a monster used for? At first I thought it was save DCs for their spells, but that's just 10 + Applicable Stat + Spell Level.

[Mauril]

Dispel checks, mostly.

[Talon Stormwarden]

Durations, ranges, area of effect, damage...lots of stuff.