As for the spirit turtle, its cultivation speed was far too slow.
But the spirit turtle's help to him was far from limited to battle.
The Black Tortoise Carapace it had refined back then had been painstakingly collected by the Holy Son of Tiandao Palace, and it recorded secret methods capable of further controlling the Heaven and Earth Furnace.
From it, Su Shi'er had already obtained two secret methods.
One was the Blood Refining Method, which deepened his connection with the Heaven and Earth Furnace and allowed him, when needed, to store the Heaven and Earth Furnace within his own Dantian Small Universe.
The other was the Xuantian Spirit Guiding Art. With this secret method, he could stir the spiritual essence of magical treasures, thereby uncovering their true functions and finding the specific methods to control them.
Unfortunately, the Heaven and Earth Furnace's power far exceeded Su Shi'er's expectations.
Over the years, Su Shi'er had often tried using the Xuantian Spirit Guiding Art to stir the Heaven and Earth Furnace.
Yet he had never found any particularly powerful method of controlling it.
Instead, mastering this secret method had made it much easier for him to control other Magic Treasures and Divine Weapons.
But that was not important. The key was that the contents upon the Black Tortoise Carapace had yet to fully reveal themselves.
It was foreseeable that when the spirit turtle's cultivation advanced further one day, he might obtain other wondrous methods as well.
So long as it gave him a little more understanding of the Heaven and Earth Furnace and a little more control over it, it would all be worthwhile.
Under such circumstances, raising the spirit turtle was no problem at all.
Not to mention that the spirit turtle itself excelled in defense, having refined both Black