The term 'kind of viper' can be summarized by two crossword solutions: ADDER (5 letters) and HORNED (6 letters). An ADDER is a venomous snake found in Europe, North Africa, and parts of Asia. It is the only venomous snake native to Britain and Ireland. The HORNED viper is a species of venomous snake found in the Middle East and North Africa. It is known for its distinctive horns above its eyes. Both of these snakes are members of the Viperidae family, which includes some of the most venomous snakes in the world.