The Adeptus Mechanicus is a group of humans who think being human is weak and disgusting and that becoming a machine is pure and holy. In a setting where humanity is forced to worship the Emperor of Mankind as a literal God, the Cult Mechanicus has the most religious freedom anyone could ask for and their interpretation of the Imperial creed is somewhat skewed so the Imperium can keep these nerds happy. Without these nerds, humanity would not be able to maintain its technology.
The Techpriests of Mars have a massive collection of war and this lore article is really just going to be in introduction.
The Adeptus Mechanicus revere a God called the Omnissiah - an all knowning God of Technology and Knowledge. Knowledge and obtaining information is seen as secret and while the Mechanicus and the rest of the Imperium's goals are often the same, some of their members would not hesitate twice in sacrificing the lives of Imperial citizens if there was a highly probable chance of any knowledge being retrieved.
Because the Emperor knew things that nobody else did and his coming coincided with a Mechanicus prophecy, the Cult revere the Emperor as the Omnisiah. Especially since he is now kept alive by the machinations of the Golden Throne.
Without the Adeptus Mechanicus neither industry nor war would be sustainable for the Imperium of Man and it would be the doom of the human race.
The Adeptus Mechanicus have many sub-factions that fight on their behalf. The picture above is shown a Skitarii army. This is a kind of enhanced soldiers army.
Personally, they are an Imperial army and I would love to collect, but it is also one that I have never fought against because they had not yet had enough models and rules for them!
I needed to do an introduction for the Adeptus so I can post some follow-up contact that will be coming soon!
Thank you for reading!