Guardian spirit

The lion dog spirit is a chimerical creature from the Spirit World.

History
On her way to Hai-Riyo Peak to return an injured dragon bird spirit chick to its nest, Korra came across three dark lion dog spirits. Though frightened at first, Korra recalled Iroh's advice to keep a positive attitude in the Spirit World, and concluded that the spirits merely looked scary. Happily introducing herself to them and stating her objective, the spirits turned light again, becoming friendlier. They them guided Korra to the dragon bird spirit nest, one of them even carrying her on her back. They witnessed Korra returning the dragon bird spirit, and its merging with three others to form a giant dragon bird spirit. The lion dog spirits followed Korra and dragon bird spirit to the Tree of Time. After Unalaq revealed himself keeping Jinora's soul hostage, the lion dog spirits turned dark and hostile again, growling at Korra. They followed Korra as she opened the Northern spirit portal, and attack her as she tried to go after a dark Furry-Foot and Jinora. Tossing Korra around a bit between themselves, they let her down as Unalaq moved in to attack her spirit. They later watched as Korra was rescued by the dragon bird spirit, and began chasing after them, before the dragon bird spirit took flight.

Anatomy
The lion dog spirits are mostly blue, and are big enough for a human to mount on. Their paws and face are of a lighter shade of blue, with a white area around their mouths and eyes, pink nose, and yellow eyes. The top of their heads is similar to a conical hat. As dark spirits, their entire bodies are of a dark shade of blue, save for their eyes, which turn pink, and their lips, which turn read. Their manes also become sharper.

Behavior
In their normal state, they're friendly and helpful, readily sniffing and licking those who they considered friendly. They're also interested in those individuals, following them through great distances. As dark spirits, they're aggressive, growling menacingly at those who come near them.

Connection
The lion dog spirit appears to be inspired by Chinese guardian lions, and their Japanese counterparts, also called "foo dogs". They are most commonly seen in statues in temples, believed to be protective entities, usually depicted in pairs, representing many dualities that arise from the yin-yang concept.