Warforged

Warforged are an exceptionally rare species of sentient automatons that originated from the The Halls of Kaz Nardoth. The Artificer's in the halls of that kingdom worked on creating automatons with more knowledge and feeling than ever seen before, and in a surprise to themselves - accidently created a sentient automaton.
After trying to cover up their work the first Warforged, the Phantom Steel King, escaped from his cell before he could be destroyed and spread the knowledge of how he came to be amongst the masses. With the secret now out, and the papers he had stolen been copied and spread amongst the black markets, the exceptionally wealthy and those with the tools and knowhow began to comission their own Warforged.
With possibly less than 500 in the entire world, the Warforged are the rarest race in Estellia.
See the official sourcebook for more details! Visual details can be changed upon discussion with the Dungeon Master.