Here is the full list of all 43 Chronos: Before the Ashes achievements.
Unlock Everything
Complete the Game at age 21 or younger
Complete the Game on HEROIC
Complete the Game on any Difficulty
Complete the Game on ADVENTURE
Defeat the Dreamer
Defeat the Labyrinth Guardian
Put 30 Attribute Points into Arcane
Acquire the Labyrinth Scythe
Return a Keepsake to the Krell King
Exchange your Starting Weapon with a Krell Version
Acquire the Shadow Stone
Defeat the Pan Guardian
Acquire the Pan Shield
Read 10 Books or Scrolls
Put 30 Attribute Points into Agility
Upgrade Any Weapon to Level +5
Defeat the Red Widow
Solve the Flautist Riddles
Meet the Pan Flautist
Acquire the Lightning Stone
Acquire the Pan Spear
Craft a Krell Mace
Defeat the Stone Golem
Put 30 Attribute Points into Vitality
Defeat the Krell Guardian
Acquire the Sun Stone
Create a Rare Dragon Shard
Acquire the Krell Hidden Weapon
Acquire the Krell Shield
Upgrade Any Weapon
Read 5 Books or Scrolls
Acquire the Krell Hammer
Put 30 Attribute Points into Strength
Travel to Ward 16 by Way of the Mirror
Unlock Your First Trait
Acquire the Fire Stone
Meet the Krell Blacksmith
Open a Dragon Inscribed Box
Acquire a Dragon Heart
Upgrade Any Weapon to Level 9
Complete the Game in NG+ Mode