The Numidium is a colossal humanoid golem from The Elder Scrolls; both video games the Elder Scrolls II: Daggerfall and the Elder Scrolls III: Morrowind involve the Numidium, or at least its concept, as a central plot element in each games' story.
First Numidium (Anumidium)
The Numidium was constructed by Dwemer artisans during the First Era and was intended to serve as a god of sorts for the Dwemer people. There are many accompanying theories that it was built to allow for Mortal Plane transcendence. The original power source was the Heart of Lorkhan, which the Dwemer had enchanted using Kagrenac's Tools: Keening, Sunder, and Wraithguard.
The Numidium was gifted to Tiber Septim by the Tribunal in return for Morrowind's semi-autonomy. The Emperor ordered his Imperial Battlemage, Zurin Arctus, to construct a control device known as the Totem of Tiber Septim. The Tribunal did not include a power source, so a new one called the Mantella was created and infused with powerful life energy.
The Numidium was used by Septim to subjugate all of Tamriel, including the neutral Tamrielic royal families, in an attempt to eliminate anyone not absolutely loyal to his rule. An enraged Zurin Arctus attempted to halt the Emperor's mad conquest. In the ensuing chaos the Totem was lost, and the Numidium was shattered.
In The Elder Scrolls II: Daggerfall, the player eventually recovers the Mantella and the Numidium is activated by an unknown person. As a result, a "Dragon Break" (a spacetime anomaly) occurs. Subsequently, multiple endings of Daggerfall occur simultaneously: the Kings of Lliac Bay are defeated preventing a major war, Orcs become citizens of the Empire, the King of Worms becomes a god, and the Underking dies. The Numidium is completely destroyed as a result.
Second Numidium (Akulakhan)
The second Numidium (named Akulakhan) is a reconstruction, of sorts, of the first Numidium; as detailed near the end of The Elder Scrolls III: Morrowind, it is powered by the Heart of Lorkhan, a powerful magical artifact in the Elder Scrolls universe. Its construction was overseen by the antagonist Dagoth Ur. He states that his goal is to cover the entirety of the world with his Blight, a deadly disease that Dagoth Ur uses to both infect, convert and control, citizens of Morrowind, so all mortals could be connected to the Heart and be controlled by Dagoth Ur.
But, in 3E 427, the Nerevarine arrived in Vvardenfell from the Imperial City prison, recovered Kagrenac's Tools and led an assault against Dagoth Ur. Using the power of the tools, the Nerevarine was able to destroy the enchantments on the Heart, killing Dagoth Ur and making Akulakhan literally fall apart, most of it fell into the lava below.
- A Dwemer depiction of their proposed Numidium can be viewed here.
- It is possible that Numidium may have been named after the city Numidia.