Dreadnought

Dreadnoughts are the siege walkers of the Space Marines. They're piloted by a Space Marine who almost died, but survived only with the Emperor's grace and loads of plot-armor favoritism. If the apothecaries managed to save his life, he has the option of being interred into a Dreadnought and pilot it from the confines of his armored sarcophagus.

Dreadnoughts are incredibly tough and their pilots even tougher, they're totally fearless and won't mind that they're gonna die a painful death under the hail of anti-armor fire and the only real way to totally kill a Dread is by blowing it all up or destroying the Sarcophagus.

HOW TO MAKE A DREADNOUGHT

1: take 1 badass Space Marine

2: shoot him in the kneecaps and a couple of his lungs

3: leave the dying body on the doorstep of some Adeptus Mechanicus guy

4: ???

5: PROFIT!!! DREADNOUGHT!!!