What do the hist even do? Where do they come from? Did they create the argonians? I even read somewhere they perceive time differently and are psychic.

The Hist are sapient trees.
Apart from the Ehlnofey they are the only survivors of the war of the twelve worlds in the Dawn Time.

It is likely the Hist took a race of small reptiles and molded them into the Argonians.
The Hist has a great amount of control over the physical appearance and mind of the Argonians.

Hist are telepatic and connected via the roots, they are all one big hivemind though it is possible for an individual Hist to break free of this and go rogue.
Hist do not seem to perceive time as linear and probably worship Sithis.
Thats about all we know of them.

To note, the Hist acknowledge Sithis was the push who got the sitting ball rolling, so all reference to worship is conjecture by fans.

Notelhnofey

At some point someone mentioned the Hist transcend kalpas or at least are from another, but I have no idea what their evidence was. I think it just made sense in the context of the other theories everyone was going over.

This is the Lore Forum. Making up insane theories for fun is kind of our thing.

Anyway, I'm not sure about transcending kalpas, but the end of Lord of Souls (to me at least) suggests they and the Argonians might have an I'm-My-Own-Grandpa type thing going on.