Having ruled the world in their time, this kind of ambition would obviously not get away.
And with their current power, even if the mortal men had numerous advances in weaponry, they would still not be able to stop them.
The best example would be how he was still fine even when those small cannon bullets were fired upon his head.
General Xue knew that if it was before when he was alive and had the meagre strength which he had before his death, then just even a single fire from the hand cannon would have been enough to take his life.
And that was even after his strength was enough to withstand the onslaught of tens of men against him.
But with this weapon, which he had faced right now, he was sure that he won't have even known how he died if he didn't have his current strength and his indestructible body.