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