The hive queen of an alien species was captured and used for experimentation. Her brood adapts rapidly to its environments to vastly enhance their survival rate, so the individual spawns were isolated in their own unique cells.
Athamagest was the worker spawn subjected to the most intense mutilation and experimental drug testing; in response, it developed rapid regeneration, caustic blood, its own ability to spawn children, and more undiscovered mutations.
In his ultimate experiment, the lead scientist implanted a unique flame into Athamagest's body that, if absorbed, would bestow the owner immense extraordinary power. The experiment was successful; however while connected to the hive, Athamagest's only desire was to escape, and this manifested in the flame granting it the ability to travel between dimensions.
Now, Athamagest possesses its own will, and breeds a hive army of its own on other worlds with the ultimate goal of returning to free its Queen.