Here is the full list of all 31 Aegis Defenders achievements.
Complete Game on Insane Difficulty
Purchase all items
Complete Area 6
Complete Game on Hard Difficulty
Collected All the Relics
Complete Area 5
Found Kobo and the Clarent
Rescued Shreya
Complete Area 4
Zula Joined the Party
Defeat the MadXArmor
Complete Area 3
Purchase 15 items
Defeat the (KS) Breath Dragon
Obtained The Blood of A God
Earn 50 RP from Dialog Choices
Complete Area 2
Kaiim Joined the Party
Defeat the Zanoh
Collected 15 Relics
Killed 300 Enemies
Purchase 5 items
Complete Area 1
Killed 200 Enemies
Complete an entire area without dying
Discovered Aegis
Collected 5 Relics
Killed 100 Enemies
Bart Joined the Party
Clu Joined the Party
Complete the game without dying