Twelve kingdoms possibly derives some loose inspiration from the Wei, Shu, and Wu Chinese kingdoms of the 3rd century CE which are popularly referred to as the Three Kingdoms.
The Three Kingdoms (AD 220–280) were Wei (魏), Shu (蜀), and Wu (吳). The Three Kingdoms period, part of the Six Dynasties period, followed the loss of de facto power of the Han ...
I touch on this in my answer to your other question. Eastern and Buddhist myths often use the cosmic egg to explain creation. In Chinese mythology, it is Pangu who hatches from the egg. In Hindu mythology, it is Brahma. In Buddhism, Buddha himself is depicted as hatching from the egg as seen below.
The myth of the World Tree is another that pervades ...
This is from the anime of The Twelve Kingdoms.
The 'bear' you're thinking of is a hanyuu (those able to turn to human and back), Kantai:
The memorable scene of him flipping the siege engine occurs late during the third arc, A Great Distance in the Wind, the Sky at Dawn (unfortunately, I can't recall the exact episode, but it's almost certainly 37-39.)