What is the literary term for this quotation But not by will nor valor could he save them for their own recklessness destroyed them all?

The answer is in the statement. All you need to know is what Will and valor mean.

Will in my own Words mean to have the self-control to do something one set's their mind to do ETCETERA.

Valor means boldness or determination in facing great danger

So basically it's stating that even with self-control, and the determination to save them from the danger they put themselves in he could not.