Here is the full list of all 12 SolSeraph achievements.
Defeat the manifestation of Chaos.
Defeat the Knight of Dusk.
Use all of the sun god's special abilities while in knight form.
Strike down the King of Floods.
Strike down the King of Fire.
Strike down the Queen of Bones.
Strike down the Queen of Ice.
Make sure the bonfire is not hit for 7 consecutive enemy waves.
Lead your people to build a town with at least 20 houses.
Strike down the King of Trees.
Complete a combat level without being damaged.
Defeat 300 enemies while building a town.