It is not known to evolve into or from any other Pokémon.
It is well known for its ongoing feud against Zangoose.
Seviper is a serpentine Pokémon that is usually depicted scrunched up like an accordion. It is mostly black, but has several markings on its body. It has yellow hexagon markings that run from its head to its tail, small yellow bumps where it touches the ground, and various purple scar-like marks. It has elongated red fangs that protrude from its upper jaw and fierce red eyes. Its tail is partially red and has a blade-like shape. Seviper sharpens its tail on rocks, and can use it for its former signature move, Poison Tail.
Seviper wraps around its opponents to make them unable to move. Its tail and fangs are venomous, and are used for striking and poisoning prey or enemies. It has been bitter enemies with Zangoose for many generations. It lives in grassy areas.
Seviper debuted in A Tail with a Twist. Jessie was so impressed by how it beat up Ash's Treecko, that she had to capture it. After it bit off a chunk of her hair accidentally, she beat it up with her own two hands. After James and Meowth calmed her back down, she captured it in a Poké Ball. Seviper became Jessie's main battling partner replacing her Arbok. Jessie was made to leave Seviper at Team Rocket Headquarters when she headed to the Unovaregion so they wouldn't attract attention by using Pokémon not from Unova.
In Trying to Trounce Torchic, a wild Seviper attacked Ruby and Sapphire after the latter took him to her Secret Base. Her Torchic was able to put it down for the time being with its Ember barrage, but it rose back up after Sapphire fainted from an earlier wound. Ruby, seeing that there was no one around to see him fight, knocked it out cold before leaving Sapphire a letter and a change of clothes.
Seviper and its rival Zangoose share several characteristics, such as being in the Field Egg Group, residing in the same Friend Area, and being the only two Pokémon with a base stat total of 458.
Seviper and Zangoose also have the exact opposite Experience group, with Seviper being in the Fluctuating group and Zangoose being in the Erratic group.
Seviper is the only pure Poison type to not have an evolutionary relative.
Seviper is based on a viper; specifically, the habu, a type of venomous snake that was often pitted against mongooses in roadside shows. This practice is now considered inhumane and is rarely seen today. Aside from its scars, the shape of its color pattern resembles that of the elegant pitviper. The rivalry it shares with Zangoose is based on the relationship between mongooses and snakes.
Seviper is a combination of sever (to cut and detach) or severe (intense) and viper.