Here is a guide on how to unlock characters, char info.

Ratfolk Archerunnamed file 226

Golem Gotem – achievement
Unlocked by deafeating golem on the first map

The Divine

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Feels good man – achievement
Unlocked by beating the Froghemoth ( last boss on the first map ?)

The Quickling

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No trespassing – achievement
Unlocked by destroying portal in 30 seconds ( Second map )


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Dawn of the dead – achievement
Unlocked by killing 1000 zombies ( Second map)

Thanks to Saiphe for his great guide, all credit to his effort. you can also read the original guide from Steam Community. enjoy the game.