The strangers are really robots made by gremlins?
One of the T3 missions makes mention that the gremlins are apparently capable of making robots sentient and that sometimes these bots go rogue and make their own little colonies.
So what if the strangers were made with the intent of guarding the surface world and ensuring nothing above ground entered the clockworks. They're like gatekeepers of sorts and they were originally programmed to make sure no one used the arcade. But something went wrong and they, in a sense, developed their own free will and stopped obeying the gremlins.
./dramatic music
What if the knights are really robots made by gremlins? Maybe they were made with the intent of guarding the surface, originally orbiting the planet in a mobile stronghold designed for them to keep the whole planet safe...
I get the feeling we're doing a really really really bad job :D