Here is the full list of all 42 Sea of Stars achievements. It takes around 40-50 hours to unlock all of the achievements on Windows.
Build your own town
Defeat Stormcaller
Learn Captain Klee'shaë's true identity
Defeat the Dweller of Woe
Defeat Romaya
Defeat Chromatic Apparition
Break a total 50 locks in battle
Get sent to Sleeper Island
Defeat Forbidden Cavern's boss
Find the Solstice Amulet
Defeat the Dweller of Torment
Defeat the Leaf Monster
Defeat the Acolytes
Fight the Dweller of Strife
Defeat the Toadcano
Attend the ceremony
Learn Seraï's true identity
Defeat Meduso
Defeat the Triumvirate of Eminence
Meet Arty
Defeat the Dweller of Dread
Defeat Elysan'darëlle
Defeat the Watchmaker in a game of Wheels
Have dinner at the Golden Pelican
Defeat the Gun Goddess
Defeat the Sea Slug
Defeat the Elder Mist for a second time
Defeat Croustalion
Free Duke Aventry's soul
Build a Spa, an Inn, a Shop and a Fishing Hut in Mirth
Bring all Conches to Mirna in Docarri Village
Catch every fish species at least once
Achieve pro rank in every single Quiz Question pack
Fulfill the ultimate wish
Defeat the Fleshmancer
Bounce a moonerang 25 times in a row
Defeat 10 bosses with Artful Gambit relic on
Cook every recipe at least once
Unlock all combos
Listen to all of the campfire stories
Find every single treasure
Use the spa in Mirth with all 6 playable characters