Phaya Naga is a large serpentine entity said to inhabit the Mekong River in South Asia. The animal's rarely ever sighted, and instead is said to be responsible for "Naga Fireballs" which are balls of fire which seem to shoot out of the river at night. Phaya Naga depictions vary, with some depictions being a sea serpent or snake-like, but the majority of depictions have it being an aquatic dragon. What the actual cause of the naga fireballs are unknown, whether it be ball lightning or hoaxes, but the phaya naga regardless has established itself as a part of South Asian culture.
Phaya Naga is distinct in Additional Creatures: Paranoia for being a mythological creature rather than a cryptid, and it shares this distinction with Akhlut and Jaculus. The reason for its inclusion is to create another parallel with Zoo Tycoon 2: Paranoia, the Zoo Tycoon 2 mod that this mod took inspiration from. Phaya Naga's design in Additional Creatures is mostly inspired behind the dragon-like depictions, but it also takes design aspects from the Quetzalcoatl: a feathered serpentine dragon in Aztec mythology. Phaya Naga was implemented in-game, where it was a venomous aquatic creature that lived in rivers and streams. Its whiskers and feathery tendrils glowed in the dark. It had the ability to fire fireballs into the air, which would either act as flares or rain back down in a barrage of fire. It was removed in Additional Creatures 2: Paranoia's convergence into a standalone, since it broke due to a lot of its code being taken from the Gigantophis. It will return with its own TLC, akin to many other creatures.