The Companion Cube Head. When a Pyramid Head got into a freakish accident with the Portal Gun, Companion Cube Head was born. The giant blade gained portal abilities letting the Companion Cube Head impale victims from extreme distances. Now it roams the corridors in search of its next victim.
When confronted with this monstrosity keep one thing in mind:
The cake is a lie.
Portal (C) Valve
Silent Hill (C) Konami