The Jiao Shen Palace has been able to continuously produce Fourth Order Flood Dragons, dominant and ruling over numerous sea clans, mainly because of this blood pool at its core.
The blood pool, according to legend, was formed from the dripping heart blood of a true dragon over countless years. The initial palace master of Jiao Shen Palace broke through the Fourth Order bottleneck and transformed into a Fourth-Order Great Demon of Transformation using the blood from this pool.
Successive palace masters of the Jiao Shen Palace always sought various Heavenly Materials and Earthly Treasures to sacrifice and strengthen this blood pool. Those flood dragons that had used this blood pool to advance to Fourth-Order Great Demons of Transformation were required to contribute a certain amount of essence blood and various Heavenly Materials and Earthly Treasures periodically to reinforce the pool.