I have infiltrated the Darkling megaship.
They are powerfully single-minded creatures; once an idea strikes, they follow it to its fullest. They have no fleet, just this one mighty warship. And quite aptly, they have named it Doom.
It carries their army, their entire race. They come to invade Earth, they call this Operation Doom.
I have seen what the megaship carries, deep in its hold: their ultimate weapon. To be used only if they cannot have Earth for themselves. Its blast will crack the ground, ignite the atmosphere and boil away the seas.
This bomb, also, is codenamed Doom.