But, Mars gave Ace and the shadows a condition that the evolution stone must immediately be used. Mars forbade them to keep them, as he didn't want any of them to hold a dangerous weapon that could cause massive destruction.
Hearing that, Ace immediately regarded the evolution stone as a weapon of mass destruction, the same as nuclear weapons. Sofia also confirmed it. If this evolution stone was used to activate an ultimate skill of a lord, the destruction that was caused would be so massive and deathly even to another lord.
At that moment, Ace realized that this operation was no longer a mission to kill a lord, but it turned into a mission to prevent the undead from holding five dangerous weapons.
He didn't know if the undead had spare evolution stones, but at least they could reduce the threat of the undead by getting them.