Strayan Template

[Serpentine]

I've let one of my players give his Huge viper companion a template, but we haven't really found any that work well. So, I've decided to make one: Specifically, a Strayan template. Aka, the template all Australian animals supposedly had. But I'm not totally sure what it should involve. I'm thinking +1, or preferably +2 CR.
I'm thinking venom, or extra-virulent venom, higher venom DC, bite damage as though a size larger, poison resistance, extra Fortitude, extra natural armour, endure elements and maybe Improved Toughness.
Any thoughts? What CR increase would this have? What else should it have?
Thanks in advance!

Also, how big would a Huge snake be?

[Deviston]

- +1HD
- Poison DC (if any) +2 and additional point of whatever ability damage dealt
- Heat Reistance (endure elements thingy for heat)
- +2 to stealth (or hide if your doing 3.5) when in desert environ
- CR+1

[Serpentine]

Good start. Any other thoughts anyway?

[Coidzor]

Hmm, may want to give them a minor bonus to con or fort saves, but it seems that the venomous vermin and animals have mostly been covered by what's been mentioned so far. I might go so far as to go to add two extra points of ability damage per time the poison takes effect instead of the suggested one for the CR+2 intent, sorta hovering between one extra point and two extra points though.

If you're wanting to have it make anything (or just about) have poison to it's attacks, it doesn't have poisonous attacks already, then its bite or non-bludgeoning primary natural weapon if it lacks a bite gains a poison with the standard HD/2+Con save. So that you can get poisonous dogs and duck-billed platypi with their spines, but things like deer or kangaroo or mules/donkeys would remain non-venomous. Or just make their primary weapon poisonous/give them a bite primary with venom.

I'm not quite sure as to the best way to determine what die type of damage it would do on a creature to creature basis though, since a flat 1d6/1d6 Con damage poison for the lot of 'em seems off as does basing the die type of Con damage on the number of HD the base creature had. Though the latter does seem to be the best I can think of at the moment, or possibly size. Maybe start with 1d2(1d3?) or 1d4 poison at the low end of the scale and progress to 1d8 or 1d10 or 1d12 at the cap with 5 levels of something like 1-3 HD then 4-7 then 8-12 then 13-17 and then 18+.

Not really sure what would need to be modeled for the merely ornery things like koalas or the nonvenomously deadly things like kangaroos and crocodiles.