Arbok - Yenra Picture Wiki
Arbok (アーボック Ābokku), known as the Cobra Pokemon, are a larger and stronger form that Ekans take when they gain enough experience.
In the main Pokémon game series, an Arbok is only acquired when an Ekans evolves. Arbok is a reptilian with purple scales over most of its body. It has lost the rattle it had on its tail as an Ekans. Like a cobra, it can spread out its ribs into a hood. On its "hood", it has a design much like an angry face. The frightening patterns on its hood have been studied and six variations have been confirmed. Each design is native to a certain region. It has a nasty bite with deadly venom. Terrifically strong, it is capable of crushing opponents by coiling its body around them and constricting. It can even flatten steel oil drums. Rather vicious, Arbok are territorial. If it encounters an enemy, it raises its head, intimidating the opponent with the frightening pattern on its body, then 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.