Here is the full list of all 24 Alwa's Legacy achievements.
Finish Pacifist Mode
Carry exactly 3 Keys, 3 Tears and 3 Petals in your inventory at the same time
Finish the game
Finish the third chapter
Finish any boss without being hit
Defeat any boss using only the Incantation of Orbis
Use Incantation of Umbra three times without touching the ground in between
Fully upgrade all magic gemstones
Find 100% secrets in all areas
Have the Incantation of Orbis fully maxed out
Transform every Save Point into a Warp Point
Help a Knight realize her true mission in life
Make it over Kloki's Bridge without being noticed once by an enemy
Finish the second chapter
Defeat Queen Eydie
Light every single torch in Ancient Catacombs
Reunite a father with his son
Defeat Desmond Grim
Upon waking up, immediately jump into the water
Defeat all Guardians
Defeat Sir Pent
Kill any enemy from above using a block
Finish the first chapter
Defeat Imprisoned King