To GMs, about the last creature in the Snows of Summer bestiary [SPOILER]

[Darrell Impey UK]

Fairly simple question really, I've just never advanced a creature in Pathfinder before.

In people's opinion, if I were to advance a greater witchcrow, would HD or class levels be a better option? And if the later, how would abilities from the witch class interact with the creatures innate abilities?

Ta.

[Lanathar]

I think witch levels because merely increasing HD will leave the creature with limited hexes and DCs.
Unless you considered the equivalent witch level to increase with HD

I believe the crow has hexes as a 5th level witch. So I would assume that it would be considered a 7th level witch for hex purposes if it had two witch levels.

I think spell like abilities would be unchanged under either option

How much were you planning on advancing it by?

[Darrell Impey UK]

Not really sure whether I will yet.

The group have offered it a deal, which is well within the ecology of the creature, and depending on how long it decides to hang around I'm considering advancing it over time. I mean, it's not like a horse or similar, it's more intelligent than most of the PCs.