Simulacrum

Simulacrum is a blanket term for "artificial life". These are constructed creatures, whether forged, vat-born, or whatever else have you, where magic and procedure were used to craft them. Some might refer to simulacrum as unnatural, a common misconception but no less prevalent and not necessarily argued with.
Races that are considered simulacrum are not necessarily abundant, but neither are they particularly rare. In the worlds they've arrived in and emerged from, there is typically a group or institute that discovers that magic spark that lets them create these things in some capacity, for better or worse. Whether that society still exists or remembers how they did it is another matter entirely - in many worlds, the art of creating life-like constructs was lost long ago, and the surviving constructs carry on looking for ways to preserve their dwindling cultures without any means to reproduce or repair their failing components.

Autognome (DDB)

Oblex (DDB)

It is not exactly known how or when the Oblexes began to mingle with the races of the world. To many, Oblexes are still just as monstrous as they've ever been... but in recent times, it would seem more and more oblexes have come to start developing... "personalities", if you will. A will and mind of their own, still driven by the need to feed, but colored by other wants and desires the oblexes of old had never been associated with. 
Oblexes as a species have origins still very much shrouded in mystery. Some creatures, those who are especially old enough to have seen the world forged and reforged time and time again, say they spawned in the wake of an Elder Evil who carried a rather unique weapon, an arcane firearm made of flesh and ivory bone... 

Meekix (Custom - Wraith)

Tiny, peculiar automatons discovered in the depths of Gadgerton and possessed with a need to be helpful. They appear wherever people need tasks finished, do their utmost to assist and – most strangely – on completing the task, die in an otherwise harmless explosion.
When the Meekix dies this way, however, the corpse fragments reassemble themselves into two new Meekix. One assumes the identity and capabilities of the original and resumes exactly where it left off as if nothing had happened, seeking the next person to help, and the other – well, honestly, we actually have no idea where the other goes or what it does, but it leaves, immediately and swiftly. Probably to go help someone. Some Meekix take names to keep track of their family histories, but otherwise, they are all just named Meekix.
It’s easier that way.

• Ability Score Increase. Increase your Constitution score by 2. Meekix are used to hard labor.
• Age. A Meekix is born an adult and dies as soon as it completes the first task assigned to it, however long that takes. However, they seem obsessed with the need to die, and will often take increasingly drastic measures to complete the task as quick as possible. Keep your requests short, please.
• Size. Meekix prance around between the feet of larger races, with an appearance akin to mechanical capuchins with various irregular features. You are Small.
• Inspiring. A Meekix is nothing if not supportive. They seem innately capable of saying the right thing when it’s needed, bolstering the spirits of those around them. You gain the Inspiring Leader feat.
• Handy Helper. You gain proficiency in one skill of your choice.
• Language. You can speak, read, and write Common and one language of your choice.

Warforged (DDB)

The Warforged of Chromatia have a storied background emerging not once, but many times throughout the history of the world. Most recently, it was within the walls of Stonehaven at the hands of High Smith Mithren, a legendary dwarven smith who is renowned far and wide as one of the greatest dwarven smiths to have ever lived in all the realms.
It was his work that resulted in the creation of the living weapons, Armory and Bazelious, for better or worse. Several years ago, shortly before Shuriig's revival, Bazelious was corrupted by the Dark One's influence and went on a nigh-unstoppable rampage across the world, destroying everything in his path to make room for Shuriig's armies to march on the realm. Armory did his best to defend against his brother's attacks, taking command of the Armored Legion, but it was an effort that back then resulted in failure. After Bazelious's defeat following Shuriig's revival, time would permit Armory to rebuild the legion better and stronger than before. As for Bazelious? As his body was never recovered, it's unknown if he's dead or rebuilding somewhere out there, waiting for his opportunity to resume his madness-fueled assaults in the foreseeable future.

Simic Hybrid (DDB)