Here is the full list of all 12 HELLION achievements.
Find the source of the fragmented message
Dock the Airlock module to the Home Base
Repair and pressurize the Outpost on stable orbit
Escape from the Doomed Station
Follow Theona's footsteps in search for answers
Find clues in ruins around Burner
Find clues on Amnisos Waystation
Find out what happened to Knossos Habitat.
Find a way to Purgatory
Complete Hellion Season One