Humanity

Humanity has been the dominant species in the material realm for nearly seven millennia. They are comparatively small and weak when levied against creatures from other realms, but they have a reputation for progress and perseverance which makes them a worthy contender against nearly any extraplanar power.
Before the rise of human civilisation, humanity and their genetic cousins, the hobbits, struggled under the thumb of the dragons. However, with the discovery of magic and subsequently interplanar travel, humanity showed their potential as ample vessels for might.
The war with the dragons was a long one, but eventually, humanity's numbers and perseverance convinced the Wyrm himself to call an end to the fighting, allowing humanity to build the civilisation they so desired in peace.
However, with the rise of civilisation came only more conflicts. Humanity time and time again could not reconcile their differences, and their famous ambition became their downfall. Fights became battles, and battles became wars between nations.
Humanity's ambition for power and control finally reached its head in the city of Archon's Palm where an enormous puncture into the infernal realm was opened. Humanity realised that the realms they drew their strength from were not still wells of power, but rather conscious beings of eldritch intention. And the footholds those beings created in the material realm wouldn't be closed so easily.
Humanity, being susceptible to the influence of the realms, slowly twisted into reflections of the power they coveted. Devils, Wraiths, and Faeries turned against their fellow man, and a new war began.
The warrior queen, Sword-Saint Kormir orchestrated an exalted march into the Feywood, and the Wounded Wastes, drawing power from a new source, the celestial realm. The cradle of life itself. With her mastery of celestial power, Kormir ascended to a living thought, becoming the first of humanity's celestial pantheon.
Today, humanity lives in a shaky alliance with its sister bloodlines and neighbouring countries, slowly reclaiming the lands stolen by the realms.