Here is the full list of all 25 Ereban: Shadow Legacy achievements.
You are now part of the creed
Scan the crow in Chapter III with the visor
Use Shadow Merge to avoid a HAWK shot
Use Shadow Control on a worker
Paralyze three or more SYMs with a single mine
Learn all the lethal and mixed shadow powers
Use Shadow Vortex on three or more enemies in a row before materializing
Obtain a 'S' rank in every chapter
Obtain the Merciful medal in every chapter
Learn all the non-lethal and mixed shadow powers
Obtain the Ruthless medal in every chapter
Craft and improve every gadget
Obtain the Ghost medal in every chapter
Open the secret room in Chapter VI
Help Helena to find out what happened to her family in Chapter V
Unlock the Darkness Ending
Unlock the Light Ending
Unlock the Hope Ending
Complete Chapter VI
Complete Chapter V
Help Gerel escape with his cell in Chapter IV
Help Kelsa and all her team in Chapter III
Complete Chapter II
Get detected by three or more SYMs at the same time
Complete Chapter I