Full list of all 9 Dark Siren achievements.
The base game contains 7 achievements, and there are 2 DLC packs containing 2 achievements.
Complete the Extra ending
Complete the true ending
unlocked the skin and change the skin.
Complete the normal ending
opened the locked door.
captured by the Dark Siren.
First encounter with Dark Siren.
Two Sirens, double the joy... no, double the difficulty.
I was trampled by the giant siren's feet.