To unlock the Seer class in Tribes of Midgard, players must exit their worlds using the Bifrost structure at least ten times. 

The Bifrost structure is a unique building that will allow you to escape your worlds with all of the golden horns you gathered up to that point. You will also need to use this structure ten times to unlock the Seer class, but before you can do either, you will need to unlock the Bifrost structure.

To unlock Bifrost, you must survive to around day four and kill your first Jotun. If you have trouble taking down the Jotun, having at least one player who is a hunter and two others with sword or axe weapons all attacking the Jotun at once will do the trick.

After the Jotun goes down, you will then be able to use the Bifrost. However, we recommend getting a few golden horns by slaying enemies before you do; we also recommend farming camps for golden horns, etc.

But if getting Seer is all you want, simply leave using the Bifrost shown above and repeat the same steps nine other times and you will unlock the Seer. 

Check out some more Tribes of Midgard guides at Pro Game Guides!