A subtle karma system has been discovered within Metal Gear Solid V: The Phantom Pain that alters the appearance of Venom Snake over time.

The karma system (or "demon level"), is determined by the choices you make in the game.

Negative choices, such as killing people, harming animals and developing nuclear weapons result in your demon level increasing, causing the shrapnel spike on Snake’s head to grow.

However, positive actions like extracting animals and child soldiers, or visiting Mother Base’s zoo, will mitigate negative actions causing the spike to shrink.

There are three demon levels. The first results in the regular spike that Snake starts with. If you gain 20,000 demon points, the spike will grow even longer within a cut scene. Upon earning 50,000 demon points, the spike will grow longer still and Snake will be permanently covered in blood.

The demon level can be raised and lowered as many times as you like and appears to have a purely aesthetic effect.

For a complete overview of the system, check out AlxCj’s guide on GameFAQs.