Evolving monsters and where to find them

[Natan Linggod 327]

A common trope I've been seeing in the manga I've read lately is 'evolving monsters'. That is to say, monsters that grow into greater more powerful forms after meeting some prerequisite condition.
Monsters in this case often includes humanoids like goblins becoming hobgoblins then ogres for example.

I'd like to incorporate that idea more fully into a home game. So I thought I'd see if there are any creatures that already do this in PF.

The closest I've found is the Nabassu with it's growth point mechanic.

Are there other creatures I'm unaware of that have a built in 'evolve' mechanic?

[avr]

Barghest to greater barghest works the same way as the nabassu. True dragons gain power with age. Many creatures gain 'character levels' which transform them dramatically, especially in the case of the dragon disciple (& a bunch of similar PrCs which didn't make it over from D&D).

[Natan Linggod 327]

ooh! I'd forgotten about barghests!

I know I can add class levels and just more HD/char levels to stuff, but I'm hoping to work out a more generic 'growth/evolution' system that I can use.

Of course , 'in world' people will know the 'rules' for monster evolution and will adjust accordingly.

For example, (knowlegable) people know that abundance of prey combined with certain mystic concordances in a swamp can cause troggs (swamp goblins) to sometimes grow into trolls, so smart local rulers hire mercenaries(adventurers) to cull the goblins/prey/both during certain times to prevent it.

[Decimus Drake]

Sounds a bit like Goblin Slayer.

[Chad Nedzlek]

This is sort of what templates are for. They vary in complexity, from the hum drum "Advanced" and "Celestial" to things like "Dark Tapestry Creature". There are quite a few existing ones spread around the various books in Pathfinder, and you can always create your own in a similar fashion.

[Kerney]

Adding/looking at eidolon evolutions could definitely be a way to go.