A series that fundamentally shaped how I think about shapeshifters within a mythical framework is the 'Others' series by Anne Bishop. It isn't about werewolves or traditional shifters in the urban fantasy sense. Instead, it builds an entire world where the 'Others' are ancient, terrifying earth natives—elementals, vampires, and shapeshifters who take forms inspired by global folklore, like ponies that are really flesh-eating predators drawn from Welsh myth. The lore isn't just a trait; it's the bedrock of society and power dynamics. The fear and reverence for these creatures feel earned and deeply woven into the world's history.
For something with a more scholarly approach to lore, 'The Wolf in the Whale' by Jordanna Max Brodsky is staggering. It's a historical fantasy where Inuit shamanism and Norse mythology collide. The shapeshifting here is spiritual and literal, with characters transforming into whales, wolves, and bears. It treats the mythologies with profound respect, presenting them as competing, equally valid cosmological forces. The transformation scenes are less about body horror and more about a complete dissolution and reformation of identity within a cultural and spiritual context. It's a demanding read, but the mythical integration is unparalleled in its seriousness and scope.
If you want mythical creature lore that extends beyond Western European templates, 'The Daughter of the Moon Goddess' by Sue Lynn Tan explores celestial Chinese mythology, with transformations involving dragons, phoenixes, and other divine beings. The shapeshifting is elegant, magical, and tied to deep familial and celestial legacies.