This Labor is all about upgrading the Leviathan Axe to its final state. Seeing as this unlocks new skills for you, you'll be completing this naturally over the course of the game with the exception of the final level. You upgrade the axe with the Frozen Flame Resources found around the world, their locations can be found in the table below.
Frozen Flame #1
Upon meeting Brok for the first time at The River Pass
Fronze Flame #2
Upon defeating the Ogre on the way to the Mountain for the first time
Frozen Flame #3
Upon defeating Járn Fótr in the Heart of the Mountain
Frozen Flame #4
Upon defeating Magni and Modi at Thamur's Corpse
Frozen Flame #5
Purchased with Chilling Mists from Brok's Shop
Chaos and Conflagration
Chaos Flames Collected  / Blades of Chaos Upgraded 
Like the Leviathan Axe, this Labor is all about upgrading the Blades of Chaos you obtain late in the journey. There's only four Chaos Flames to collect and you can't purchase the last upgrade until you finish the Journey. You'll find the locations of the Chaos Flames in the table below.
Chaos Flame #1
Upon defeating the Bridge Keeper in Helheim
Chaos Flame #2
Upon defeating the Grendel Trolls in Týr's Vault
Chaos Flame #3
Upon defeating the Hel-Traveller during your escape from Helheim
Chaos Flame #4
Purchased with Raging Inferno from Brok's Shop
Justice and War
Bring Týr's Offering to Brok and Sindri
You'll need to complete the Hammer Fall quest as part of the Wayward Spirits Favor to receive Týr's Offering. Once obtained, bring this back to Brok or Sindri to complete the Labor.
Hearts of Stone
Bring the Ancient's Heart to Brok or Sindri
Ancient Armor Set Recipe, 350 XP
When you travel to Alfheim for the first time, you'll encounter your first Stone Ancient. Upon it's death you'll receive an Ancient's Heart, bring this back to Brok or Sindri to complete the Labor and unlock the Ancient set in the Shop.
Following the destruction of the Greek Pantheon, Kratos hides himself away in the Norse realm Midgard. Upon the death of his beloved, Kratos and his son begin a journey that will change them forever throughout the Norse realms. As a mentor to his son, he must be a guiding light but the burden of his past still looms over him.
The most complete guide for God of War features everything you could wish to know during your time in Midgard. A step-by-step walkthrough featuring every collectible, treasure map and more illustrated with gorgeous screenshots.
Full walkthrough of the main storyline.
Coverage of all Sidequests.
Detailed strategies on how to defeat every optional boss.
Find every Treasure Hoard.
Every collectible uncovered.
Detailed information on character builds for Kratos.