Spirit naga

Spirit nagas are the most powerful type of naga. They have a human female head on a snake body and are spell-casters.

Combat
Spirit nagas meet their foes boldly.

Novel Appearances
A spirit naga was seen in The Harpers Series book three Red Magic. Here she was the personal assistant of the Zulkir of transmutation Maligor. She was depicted as mostly humanoid with the only distinction being that she had a snake tail instead of legs and a small forked tongue.

Except for her natural form, she had the abilities to morph into others shapes. Maligor used that ability, to replace the manager of Thays gold mines, thereby taking control of them. This was all part of a complicated plot with the purpose of getting rid of the zulkir of necromancy, his most powerful adversary.

In all of this she showed great loyalty to him, and an ability to commit to a complicated plot, both of which indicated that she was not chaotic evil. More likely she was of a neutral evil alignment.

(it is more plausible that Maligors servant, Asp, is a Shinomen naga of the asp kind, from the Oriental Adventures, in the book she is referred to as a "Daga")