The Yin body had created a black membrane around Noah's heart when he was still a human. Then, when he had fused himself with a Cursed Dragon, the membrane and his heart had merged to become a single organ.
That had improved Noah's healing abilities. His injuries would close far faster than those of similar beings on the same level. Also, it made his heart one of the strongest organs in his body.
Noah needed a place inside his body where he could put the organ containing higher energy. He couldn't leave something capable of such gravitational pull near tissues that it could break apart easily.
Of course, that was relative to Noah's situation. Every tissue in his body surpassed the human standards, but he was dealing with an organ meant to contain a star.
He had to make sure that he wouldn't incur ugly repercussions after the transplant.
Nevertheless, Noah had yet to create the actual organ, so he didn't spend too much time planning what would come after that.
