Potions of Infravision give the user infravision for a short time. Infravision is the ability to see in the dark but its in game usefulness if doubtful as it is easy to see at night without it. It's only use is to make NPCs slightly more noticeable at night as they are highlighted red for characters with infravision. Potions of infravision can be bought and sold at stores as well as looted from dungeons and bodies.