Brontoliths were born to endure. With no natural weapons other than sheer size and strength, they mostly relied on their armored skin as protection from predators. Open wounds were a common denominator throughout their existence, and viruses, bacteria, and more exotic lifeforms often made their way into the Brontoliths bloodstreams. None of these harmful organisms managed to cause any damage, however. The Brontoliths immune cells latched on to anything foreign and either destroyed or assimilated it. This trait was further enhanced by the Swarm, allowing Ultralisks to thrive in the most toxic or deadly environments the galaxy has to offer.