Two Doors

The sheer tenacity and perseverance that he displayed were unparalleled.

A large hole in his Body with damaged lungs, heart, and spine.

Even if he had copied some healing techniques, he was not able to heal lethal wounds fast enough before the blood loss knocked him out and then killed him. On top of that, even if it was fast enough, it didn't have the fuel to heal his Body. Regenerating large amounts of tissue needed an equal amount of nutrients, organic matter, and other compounds.

This sort of wound was a death sentence.

Any other Master would have accepted death and simply died.

Not Ieyasu.

He saw a source of all the nutrients and compounds that he would need to regenerate and heal his wound right before him: the Harbinger herself.

The issue was that he was too weak to fight her with such a lethal wound. There was no way that she would allow him to assimilate her Body to heal his wounds.