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.
View all the Polaroids in the game.
Collect all the tapes in the game.
Build a small tower in the Culling Grounds.
Reunite the spectators of the Cull.
Have a nap in the Transport Room tent.
Give Hermie a new home.
Complete every cog puzzle and unlock Sebastian's safe.
Obtain the Grasp.
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.
Kill every Wizgog in the Culling Grounds.
Pop a Wizgog without using the Arbalest.
Play the Cosmic Key.
Blast 10 corpses with a single Arbalest shot.
Dismember 44 limbs.
Activate the Easter Egg.
Kill the captured Wizgog.
Collect, view, and read all the lore in the game.
Clear the crypt without using the flashlight.
Build a large tower in the Culling Grounds.
Read all the stories of the people of Ember.