The Poison Naga is a rare enemy that only appears in the Dawn of Souls and other succeeding versions of the original Final Fantasy. It can be found in the ocean on the Overworld level of the Hellfire Chasm. It usually uses the Poison Gas attack and flees from high level parties.
Naga (Sanskrit: नाग, Nāgá) is a deity of entity taking the form of a great snake—specifically the King Cobra—in Hinduism and Buddhism. For female counterparts, they're called nagi.