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.
Pop a Wizgog without using the Arbalest.
Have a nap in the Transport Room tent.
Build a large tower in the Culling Grounds.
Build a small tower in the Culling Grounds.
Kill every Wizgog in the Culling Grounds.
Read all the stories of the people of Ember.
Send a corpse down the shaft in the Tower of Cogs.
Complete every cog puzzle and unlock Sebastian's safe.
Dismember 44 limbs.
Obtain the Grasp.
Collect all the tapes in the game.
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.
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.