Viper
Almost all vipers have ridged scales, a well built body with a short tail and, to make room for the venom glands, a triangular-shaped head.  Their slit-shaped pupils can open wide to open most of the eye, or close almost completely.  This helps them to see in a wide range of light levels.  Vipers are nocturnal, meaning that they sleep in the day and wake up at night to go hunting.