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