Seviper, the Fang Snake Pokémon. Seviper shares a generations-long fued with Zangoose. Its sword-like tail can slash foes and douse them with poison.
– Nicholai’s Pokedex
Seviper is the snake Pokemon in Gen III, despite there already being a poisonous snake-based Pokemon in Arbok and Ekans. Seviper doesn’t evolve though, and it’s the only pure Poison type that doesn’t have an evolutionary relative. It’s known for its eternal rivalry with Zangoose, though strangely, Seviper and Zangoose can breed. Speaking of breeding, Seviper for some reason is in the Dragon egg group.
In the anime, Jessie had a Seviper. It was a wild Seviper that chopped off Jessie’s hair (by accident), she got very angry and beat it up (it fainted) and caught it in a Pokeball. It’s a bit strange that Jessie had an Arbok, and now she got a Seviper, I guess she had an affinity to snake Pokemon.
Also in the English anime, Seviper was incorrectly claimed to be an evolution of Arbok in the Pokemon Trainer’s Choice.
Stat-wise, Seviper has good Attack and Sp Attack, but not very good defenses or Speed. In the Pokemon TCG though, there’s a Seviper card that’s pretty good; I have it in my psychic deck. It’s a Basic Pokemon, and has the attack Paralyze Poison, which on a coin toss of heads, paralyzes and poisons the defending Pokemon.