Capítulo 1257: The Next Best.

As long as a warrior with the heart of a life tree possesses Origin energy, they will never die. They can even recover from having their body smashed to pieces. 

To be honest, it is a slight exaggeration to say that warriors with the heart of a life tree can never die. There is a limit to the recovery power of that divine ability. For example, the explosion of a star will destroy a warrior and the heart instantly. 

Then again, trying to withstand the explosion of a star is going overboard. As long as warriors are not exposed to that kind of massive and instantaneous destruction, they will never die. Unfortunately, it is not allowed for warriors. 

Legion doesn't need the heart of a life tree either so they turned to other alternatives. It is just that their choices have been drastically reduced because of the type of dragon heart he has.