while roaming around Old Nevada, a abandoned country taken by the Grineer but liberated by The Tenno, you then see dead Grineer, you then investigate and see a paper that resembles a Centaur…you then are blasted away by a giant robotic roar, you look up and see the 1000-THR “Earthmover”, a Supreme Machine of such size. And it then speaks in Japanese:

"より高い脅威が検出されました。説明してください。さもなければ解雇されます。" (HIGHER THREAT DETECTED, EXPLAIN YOURSELF OR BE TERMINATED.)

then the giant War Machine raises its lighting spear, you better do something or your toast.