Bulgasari is a creature that eats iron and swells in proportion to what it consumes; its name "Bulgasal" means "that which cannot be killed." Indestructible by weapon or fire, it embodies a horror of runaway growth — the more it is fed, the larger it becomes.
The premise that it grows by devouring metal figures uncontrollable expansion. Because it strengthens the more one tries to suppress it, it carries the paradox in which restraint itself becomes proliferation.