In my world, manticores are large, feline-like predators native to the tropical forests and shrubland of Svargalya (a region of my world roughly equivalent to the Indian Subcontinent and Himalayan regions of Asia). While extremely similar to big cats in many ways, they (along with sphinxes and similar beasts) are actually primates, distantly related to monkeys such as baboons and mangabeys.
They are larger than a lion but smaller than a tiger, with mottled, red-and-brown fur. Almost everything about them is feline. Their overall figure, musculature, long tail held up, and clawed feet all point to them being a big cat. Males even have a shaggy mane that flows over their neck and upper back. However, their face is undoubtedly that of a primate. In fact, aside from the monkey-like nose, it's very similar to a human's. It's teeth are jagged and sharp with massive, curved canines, and unlike other mammals, are constantly replacing themselves like a shark's. Often, multiple rows of teeth will be exposed at a time. Their tail is covered in long, porcupine-like barbs that are filled with a paralyzing venom used to easily subdue prey. Only elephants and monoceroses seem to be immune to the venom's effects.
The most disturbing thing about the manticore is that, as a species, they seem to enjoy humans as prey. They also often target big cats like tigers and leopard. There is possibly some sort of nutrient or energy that these animals have which manticores crave, but the real reason why they almost exclusively hunt other predators is unknown. Their vocal capabilities are impressive, and they are known to be able to near-perfectly mimic the sounds of many other creatures, including human voices. Its believed that because they can mimic different individuals, they must also have great memories. Their only known true call is a loud, trumpet-like bellowing, believed to be a territorial or mating call.