Goblin

Goblins are the greatest symbol of hubris on Calmira. Long ago, before even the dragons came, they were a mighty empire of long-lived savants. They knew secrets of magic and machinery long lost to time. Theirs was a life of abundance and marvels and beauty.
One of their number found a way to encapsulate talent, in order to balance out their kingdom - if, say, a painter has no use for their voice, they could sell their voice to a singer, in trade for coin or services, or for a portion of that singer's sight. A technician with a dream could trade their aptitude for tools and machines for the ability to play an instrument and learn their creativity. And none of this could be done without consent felt deep in the heart of both parties. Thus each individual could be the best, most truest form of what they wish to be.
But in every society, some are too giving, and some are too greedy. One with the power to charm someone into believing they were needing or deserving of a gift, rather than a barter - or who could be tricked into believing a lesser payment was equivalent to what they gave - could garner far more charm, and far more gifts, than ever a creature should have. In time, such a one came, and was all too successful.
With but a phrase, they gained followers who gave of themselves willfully and fully - their beauty, their strength, their voice, their intelligence. The one became a king, then an emperor, then a deity in the minds of their followers. A life well lived - but, they thought, why stop there? And they discovered that longevity could also be taken. People flocked from all over to give the best years of their lives to this ruler, this god among them. Without their beauty, their skin was sallow and wrinkled. Without their strength, their great industry could not be maintained. Without their intelligence, no magics could be used. Without their creativity, art was a worthless endeavor. Their civilizations fell to disrepair, then crumbled into ruins, and then collapsed into dust.

The goblins now are born with an undefined, unmentioned, and indescribable fire of jealousy for the other races. For some clans, it engenders rage and a need to destroy what is beautiful. For others, they will steal what they can to ensure noone else has it.
Rarely, very rarely, a goblin is born who is above the rest in some way. They have a spark of the old intelligence, or the need to create art, or to craft. These are often shunned by their fellows, if not killed outright. The jealousy towards them often leads them to flee these societies and seek their own path. They hide under cloaks and guises, pretending to be halflings or dwarves or gnomes, in order to attempt to fit in with the society they yearn for.