The dreamers are key to the spread of Oye tree (possible spoilers)

[SYED]

These tree only flourish on the right world's where the spirit is right. So I bet these dreamers could predict which world's qualify. So they would ask the Karrines to help locate and access the world.
For a long time, the dreamers prayed for the Phoenix. Their Phoenix is also a shaman in part. So I could see them believing in that hard. So eventually we would see shaman dreamers.