The Rigveda has a famous serpent. Ahi is what Vritra is called when the poets want to name what he is rather than what he does, and killing him is the central deed of the collection. So it is worth stopping at the fact that the same word, in the same corpus, also names a being who is invoked among the gods and asked for protection. Ahi Budhnya is a serpent of the deep who is on the right side.
He is thinly attested, though not as thinly as his usual companion. He appears in enumerations, most often beside Aja Ekapada, and he is asked to protect and to keep from harm. He belongs, on the standard classification, to the gods of the middle region, the atmosphere, which puts the deep he is named for in the sky rather than under the sea. Whether that is right is one of the few things about him that can be argued at all.
The pairing with a benevolent serpent tells you something about the shape of the material that the Vritra story on its own hides. Vedic religion did not treat serpents as a category of evil. It treated one particular serpent as an obstruction, because he was lying on the waters and had to be moved, and the word for serpent stayed available for a protector in the same breath. The moral load is on the act, not on the animal, which is a distinction that later traditions in the same region kept, and one that the standard translation of asura as demon tends to obscure elsewhere in the same collection.