Titanopod basilus- the C-97 Emperor Wanderer

Once more, we return to the world of C-97; the world where dragons truly fly, five-legged gazelle flee them, and, as we see here, the largest living thing roams.
This is the Emperor Wanderer. The size of a mountain, it is literally invincible. No predator dares to attack an adult directly. It can weigh up to ten thousand tons and lives longer than most animals can measure. Such is the scale of this animal that it has a set of respiratory, nervous, and circulatory organs for each 2.4-thousand-ton support leg. To top it all off, it's so gigantic that it has foreign molds and fungi growing out of its back and legs. That's right: it's its very own ecosystem.
Hundreds of animals can live on its back and legs (not too hard as something that large has to move very, very slowly) and thrive off of the fungal forests there. Although they're parasites on most other creatures, the fungus is actually essential to the wanderer's survival. The creature itself is a filter feeder, taking microscopic organisms in by the valley-load. These are circulated to the fungus which dissolve them into essential nutrients which, in turn, are injected straight back into the wanderer's system. It may sound exotic and insignificant, but the vast forests create just enough sugar and protein to jump-start this living mountain. The fungus also helps the wanderer reproduce: every year, the forests' spores carry the creature's sperm and eggs to the ground to breed new titans. Although millions and billions of these spores fly down, only one or two of them even make it into adulthood. However, the ones that aren't hunted down in adolescence will become the largest and most feared animal in existence.
Drawn with pencil on paper, edited in Photoshop