Here is the full list of all 27 The Gallery - there are Episode 2: Heart of the Emberstone achievements.
Complete the game within a 93 minute runtime.
Finish the game without harming any Wizgogs.
Give Hermie a new home.
Solve every Gauntlet puzzle.
Complete Episode 2.
Repair the Solar Engine.
Activate the Easter Egg.
Kill every Wizgog in the Culling Grounds.
Pop a Wizgog without using the Arbalest.
Kill the captured Wizgog.
Build a large tower in the Culling Grounds.
Build a small tower in the Culling Grounds.
Dismember 44 limbs.
Blast 10 corpses with a single Arbalest shot.
Reunite the spectators of the Cull.
Collect, view, and read all the lore in the game.
Read all the stories of the people of Ember.
View all the Polaroids in the game.
Clear the crypt without using the flashlight.
Play the Cosmic Key.
Send a corpse down the shaft in the Tower of Cogs.
Complete every cog puzzle and unlock Sebastian's safe.
Obtain the Grasp.
Collect all the tapes in the game.
Kill the Mother Wizgog.
Meet the Beast.
Have a nap in the Transport Room tent.