I've come up with a few, but I'll just talk about my favorite race in my world.
There is a small continent (Tah) located in the tropical/subtropical zone of my planet where the only humanoids are a turtle-based race known as the Tahween. They are known for their slow movements, long lifespan (average life expectancy is 340 Sun Cycles, which are roughly equivalent to years, but consist of ten 44-day "months"), and wisdom. They are extremely hostile to outsiders, and very few of them ever leave their home continent. Those who do choose to leave are forbidden from returning. While they are not very good at physical combat, their wisdom allows them to harness powerful water magic and earth magic to defend their homeland. Luckily, they do not use this magic for wars of aggression, since they are isolationist and do not wish to expand their territory/sphere of influence.
Their government is entirely based on who is the strongest wizard. If you want to be the Lord Wizard, you must defeat the current one to get the throne. If the Lord Wizard dies of natural causes/accident without being defeated, a tournament is held to determine who gets the throne. Their economy is basically what we would call perfect communism on Earth. Everyone contributes what they can, and everyone receives what they need. Their diet mostly consists of leaves and fruits, they will occasionally eat a small animal if the opportunity presents itself, but they don't actively seek out meat. The concept of marriage is entirely foreign to them, they do not form romantic bonds. During their mating season, it's basically a free for all. They are known to mate with multiple partners during each Vibrancy (their equivalent of our "Spring"), and they often choose an entirely different set of mating partners every Sun Cycle.
As far as religion/mythos, they believe that Tah Ara (similar to Gaia, the spirit of the planet) created them from water, leaves, soil, and a bit of magic. They abhor physical violence, as they feel it is disrespectful to Tah Ara's creation. As far as the afterlife, that's not something they buy into. They believe that the materials/energy that make up an individual are not inherently theirs, and are recycled to create new life. They have no concept of a soul, a Heaven, or a Hell.
Their staunch isolationism is a result of an attempted invasion by the Thaug (a humanoid, Rhinoceros-based race, think Rocksteady from TMNT) that took place 2408 Sun Cycles ago. The Thaug are an aggressive Imperialist race, who seek to control as much territory as possible, and only respect power. That invasion/war led to a third of all Tahween being killed or captured, but in the end, they were able to repel the invading force. As a result, the Tahween take a similar stance as the Sentinelese do on Earth, "stay the heck away from us or we will kill you before you can manage to say "hello".