So snakes, canon contract.
Users are Oro, Anko, Sasuke, Mitsuki count I think, Kabuto, I think thats it (this off the top of my head)
Summon include Manda, Manda 2, Aoda, I think theres a few others?
There is also the Snake Sake mode, which is loosely based on a 'Dragon' Sage mode maybe (at...