Night Vision

is a physical mutation that allows the player to see in the dark for a short radius.

Players with Night Vision essentially have a permanent light source that is active at all times, with a circular radius of 5 tiles.

Having Night Vision allows the player to see.

Advantages

 * Frees up a hand slot which would be taken up by a or  in the early game.
 * Very low-cost.
 * Does not take up an item slot.

Disadvantages

 * Provides a poor light radius which cannot be improved.
 * Is easily outstripped in terms of light radius by a or, neither of which are restrictively rare.
 * Every creature has advanced night vision or sensory abilities well beyond the player's ability to match, negating any stealth advantages that not having a light source may have provided.