The Black River Island is a massive island with a radius of over five kilometers hovered at the very center of the cave. The entire island was not made of ordinary rocks and sand, but black crystals. There were pavilions carved on the rocks, forming a series of palaces. A plaque that was several dozen meters long hung above the largest palace, with the words' Black River Palace 'written on it.
The entire island emitted waves of watery light. Even though it was pitch-black, it gave off a crystal-clear feeling, making the place look like a crystal palace at the bottom of the ocean, looking very magnificent and majestic. The entire island was covered by a huge, translucent black barrier, separating the lake water from the surrounding area. One could vaguely see densely packed restriction runes on the black light shield, which emitted frightening restriction fluctuations.
The entire island was a massive piece of Supreme Yin Water Jade, which was refined by Venerable Black River using some kind of mystical ability for tens of thousands of years. The entire island could be considered a massive demonic artifact at the moment, and it's extremely powerful.