Stingers are very horrible creatures that can be seen in the town of Silent Hill. They have a scorpion's stinger for a head and an armless human body. They are very tall and slow.
It uses its stinger to stab their prey, although it doesn't possess any poison. Its reach is far and wide, you almost got no chance of escaping a strike if you came face to face with this monster.
It symbolises Robert's heart attack/heart disease. From the story, the Stinger stabbed Robin in the chest.