In the new God of War Kratos has a brand new weapon in the Leviathan Axe, a change of pace from the different sets of blades that he’s used in previous God of War games. However, you will get access to the Blades of Chaos later in the game.
To get the Blades of Chaos in the new God of War you simply need to progress far enough into the story to use them. As the story unfolds in the game, a cinematic break in the action will push Kratos to retrieve the Blades of Chaos that he’s locked away.
After this mission, you will be able to use the Blades of Chaos at will as a third weapon in Kratos’ arsenal, alongside the Leviathan Axe, Melee Combat, and Shield Attacks. The Blades of Chaos feature an upgrade tree similar to that of the Leviathan Axe and can be used very effectively against certain types of enemies. The Blades of Chaos can be upgraded with Light and Heavy Runic Attacks, Blade Grips, and can be leveled to in the skill tree to unlock unique attacks for both melee and elemental combat.
The Blades of Chaos are a completely different weapon than the Leviathan Axe, giving Kratos even more range as he’s able to swing the blades which have a large radius compared to the axe.
You will receive the Blades of Chaos about halfway through God of War.