Species M-02

Species M-02 (sometimes also referred to as the Howlers, Metal Tyrants or by their own name of Silinruls) is the second sapient species of mechanical nature that was discovered by humans, its ruins found everywhere throughout the Third Sector. It is unknown if the species itself is still dead or alive (or, considering their mechanical nature, active or extinct).
The understanding of its past and nature is extremely limited and coming almost entirely from psychometric rituals. Despite managing to translate a lot of recovered blueprints and science data of Silinrul origin, Mankind is yet to actually translate their language.

Basic Information

Anatomy

Species M-02 was humanoid, with body built largely similar to that of a human. The details of their body remain unknown, however, for millenia before their (supposed) extinction, Silinruls transferred their consciousnesses to 'perfect', robotic bodies. SIlinruls enjoyed 'customizing' their bodies, leading to lack of uniformity among their body shapes, even if they seemed to mostly prefer humanoid shape.

Behaviour

Silinruls are believed to be a species of decadent slavers which conquered and enslaved a score of other organic species both before and after their machine ascension. They've mantained their social order following their ascension, which makes no economic sense - they could easily live utopian lifestyle merely thanks to their technology. All they needed was to create robotic servants to replace their biological ones.
The fact that there are no signs of Silinruls even considering that, which leads some xenopsychologists to suspect that something in their psychology demanded them to possess power over others. Whether that's true is a question that might never be answered.

Civilization and Culture

History

While the exact chronology of the Metal Tyrants is rather murky, it is believed that their empire lasted for thousands of years before they abandoned their bodies of flesh and replaced them with ones of metal and circuits. During this time they enslaved a plethora of other alien species that they put to work and had attend their every whim.
Once they abandoned bodies of flesh, the situation got clearly worse. There are signs of Silinrul empire beginning to decline from that point onward, with development of technologies such as the fleshbane weapons and the Shoggoth Plague being the result of the Tyrants fearing a revolt of their servants. Some xenologists suggest that the reason for that was the Silinrul's population growth hitting a plateau following their ascension, while the slaves continued to multiply.
It isn't clear how did the Silinrul empire collapse - civil war between the Tyrants, foreign invasion or the slave urprising are the most likely explanations.