023 Ekans and 024 Arbok

Some info about Arbok from Bulbapedia:

Terrifically strong, it is capable of crushing opponents by coiling its body around them and constricting. It can even flatten steel oil drums. If it encounters an enemy, it raises its head, intimidating the opponent with the frightening pattern on its body. If any part of Arbok's body except for the head it cut off, it can regrow the rest of it's body again in a matter of a few weeks.

Rather vicious, Arbok are territorial. They lash out at intruders with long fangs tipped with deadly venom. With a vengeful nature, it won't give up a chase after prey or an opponent, no matter how far, once it targets it prey.