Microsoft DirectX 12 is DirectX 11 with Mantle Integrated

Sources have revealed that Direct X 12 is basically DirectX 11 with Mantle absorbed, the performance increase on Xbox One is in doubt.

DirectX 12 vs. Mantle: Comparing PC gaming's software-supercharged

What are the benefits of DirectX from Microsoft? - Quora

DirectX 12 ExecuteIndirect Command Further Improves Performance

Windows Phones to get better gaming, battery with DirectX 12 - ARN

Should you be worried if DirectX 12 will be Windows 10 exclusive

Microsoft announces DirectX 12, coming 2015

Initial Vulkan Benchmark vs. DirectX 11 - AMD & NVidia in Talos

Why DirectX 12 is a game-changer for PC enthusiasts

DirectX 12 vs. DirectX 11: which is better for PC gaming