In fact, there isn't any fundamental difference between a Strathos shaman and a cleric from elsewhere other than faith.
Speaking of faith, all Shaman have a totem animal, which is the same totem animal as their tribe. By praying while holding or wearing the skin of that animal, the shaman can polymorph into that animal for a short period of time.
1st Rank (I use the term Rank, rather than level, as I find it is less confusing)
For one 1 minute Turn per level of experience, the shaman can polymorph themself into their totem animal. The skin of the totem animal must be held or worn at the time of casting. The shaman retains their reasoning capability and may end the spell before the duration at will. Otherwise, the shaman loses all other powers while the spell is in effect, but gains the natural abilities of the totem animal.
Group Skin Change
Same as Skin Change but affects a number of participants equal to the shaman's experience level. The duration is a single ten minute Turn. Same effects and rules as the 1st Rank spell.
Superior Skin Change
Same as the first level spell, but duration is 1 hour per level of experience and the shaman can speak and cast other spells as normal while polymorphed.