The Zerg Ultralisk Cavern is a massive, organic structure resembling a grotesque, pulsating hive with thick, chitinous walls and a cavernous interior. Its surface is covered in a combination of smooth, slimy membranes and rough, armored plates, with veins and tendrils visibly throbbing with bio-mechanical energy. The entrance is flanked by towering, bone-like protrusions, and the interior is dimly lit by a bioluminescent glow, highlighting the intricate network of Zerg biomass that forms the structure.