All the Latest Game Footage and Images from Left 4 Dead 2: Cold Stream This DLC is a custom campaign developed by Matthew Lourdelet, the developer of 2 Evil Eyes and eventually made official by Valve.
TL;DR: Left 4 Dead 2 RTX NTD is a ray-tracing mod by Nostalgia Drive Team enhancing the iconic 'No Mercy' campaign with 4K textures, PBR materials, and realistic lighting using NVIDIA's RTX Remix.