A billion years in the future, life on Earth has retreated underground. The surface is sterile - bombarded by UV, stripped of nutrients, and scorched by a sun 10% brighter than today. Deep within geothermal tunnel networks, a strange entity exists: Fluvimorphus lacrimosus, or “the weeping river-form.” It’s not an animal in any modern sense. Possibly descended from cnidarians, synthetic life, or even fungi, it exists as a self-replicating liquid colony - a glowing, viscous “river” that winds through rock in search of chemical gradients. Its body is made of ion-conductive gel filled with modular microbeads that act like organs, nerves, and sensors all at once. There is no head, no limbs, no brain - just waves of synchronized pulses and phosphorescent ripples across kilometers of soft-flowing matter. It feeds on sulfur, mineral ions, and fungal detritus, sometimes engulfing and digesting other lifeforms at the molecular level. It doesn’t reproduce traditionally; segments shear off and form new colonies over millennia, slowly mutating into separate identities. Sometimes, two colonies merge and exchange complex bioelectrical patterns in a kind of silent “conversation.” The creature appears to “weep” constantly - droplets condensing along its body, dripping into the stone. These may serve a metabolic purpose or be remnants of a behavior loop long lost to memory. It is not intelligent in the human sense, but its body reacts with precision and adaptability, adjusting tunnel flow, cultivating microbial gardens, and regulating heat. Entire ecosystems depend on it - parasitic scavengers, symbiotic worms, and dust-borne fungi live in its wake. Seen in the dark, it resembles a slow-moving river of cold blue light, humming with unseen charge. Fluvimorphus is not a creature - it's a process, a behavior, a rhythm etched into the rock, still flowing long after animals have vanished.