Emerging from the deepest shadows of Xylos, the Umbral Sentinel is a guardian of forgotten realms. Its elegant form, cloaked in cool blues and purples, belies a sinister purpose. Plasma arcs crackle around its icy mane as it surveys its domain with an unsettling curiosity. A potent poison sac, capable of delivering a necrotic touch, is hidden within its ethereal body. It is said that the Umbral Sentinel draws power from the chromatic convergence, a rare celestial event that bathes the alien planet in otherworldly light, manifesting as a swirling energy vortex and god rays that pierce the gloom. Magical sparkles and visually noisy particle effects accompany its every move, a testament to its potent arcane abilities and the dark, sinister tone it brings to the desolate landscape.