I just discovered Agathions recently and thought they were a fun concept. I immediately started looking for ways to bring the Agathion features to a PC level. Seems like there is an Agathion sub-domain (though it doesn't feel very "Agathion" to me). I haven't found any Agathion bloodline for Sorcerers and I don't see any templates or races that would turn a humanoid PC race into a half-Agathion, with features that one could imagine from such an ancestry such as animal ears or tail, scent ability and so on.
I know Aasimars exist, but they feel so much more like half-angels both in flavor and abilities.
Have I just missed it or is it simply not an official thing?
Blood of Angels might be the book you're looking for.
Half-celestials are gonna be your closest thing beyond agathion descended aasimars. Not sure if you know it yet but there's variant aasimars based on the descent with different racial traits and the agathion-based ones get +2 cha and con and summon nature's ally II as a spell-like ability.
Take an agathion-blooded aasimar, use some of the alternate traits to give it a more animal-like appearance, to reflect the animal-like nature of the agathions, and then apply the half-celestial template if you want to (not recommended for a PC).
Thank you all!
Blood of Angels is definitely what I was hoping for, as confirmed by the PFSRD. The agathion-blooded looks really good and with variant abilities and features, it gets even better!
Will also take a look at the half-celestial template.