[Thermo]

I was thinking of developing a new Tradition that uses the possession rules for spirits, but that is specialized towards beast possession. Any ideas on what Tradition would be appropriate? Seems like just using the Druid tradition with a twist would work ok but I was going to see if anyone had anything creative. Drain would ideally be Wil+Int (same as Druid) since the Animal Handling and Animal Training skills are Int-based.

[RelentlessImp]

Shamanism. Shamans deal with the spirits of the world - most of which are traditionally translated into beasts, representing the primal forces that bind the world into its state. Another way to go would be a twist on Voodoo and the loa.

[JustADude]

Shamanism. Shamans deal with the spirits of the world - most of which are traditionally translated into beasts, representing the primal forces that bind the world into its state. Another way to go would be a twist on Voodoo and the loa.

Excuse me if I'm utterly wrong, but perhaps African Shamanism should be looked into, as I believe that's where Voodoo got it from.

[Thermo]

Shamanistic might be an option, it uses Wil+Cha for its drain attribute which could be beneficial since the number of bound spirits is limited by Cha. Maybe cast detection spells and find any nearby animals, have a bunch of low-level bound spirits possess them and use their innate Control Animals power to take over a huge group. It'd be pretty freaky to get attacked by a huge group of amped-up devil rats or something.

[JustADude]

Shamanistic might be an option, it uses Wil+Cha for its drain attribute which could be beneficial since the number of bound spirits is limited by Cha. Maybe cast detection spells and find any nearby animals, have a bunch of low-level bound spirits possess them and use their innate Control Animals power to take over a huge group. It'd be pretty freaky to get attacked by a huge group of amped-up devil rats or something.

Oh hell yeah!

I'm totally stealing this, just FYI.
 

[Greenknight001]

The Kachina tradition is what it sounds like you are looking for. 

It is a Shaman possession tradition practiced in the PCC (Pueblo Corporate Council).  This tradition is touched on in the Denver Gamemaster's guide, but I don't remember all of the details.  The only specifics I remember is that it uses Will + Chas for drain, and they are forbidden to summon water spirits. 

Hope this helps.

[Thermo]

Wow, I'll look that one up, +1 to you sir!