A Rock is ideal -copy the idea of the ninjas, so the asteroid looks exactly like any other sterois from the outside. Brains wants invisibility, not attractive outer design.
And rememerb that there is a HUGE range of asteroid sizes -a rock a couple of kilometers long asterois is raterh useless for an habitat or a mining operation, but as a hollowed home it is a freakign big ship.
And rememerb that there is a HUGE range of asteroid sizes -a rock a couple of kilometers long asterois is raterh useless for an habitat or a mining operation, but as a hollowed home it is a freakign big ship.