Whatever the motivation, war crimes are still war crimes and are to be treated as such. In any same society, you would be executed, and your corpse displayed as a warning and attraction.
However. The gems are unusua!, I can't claim to understand them. Knowing the future has often been suggested as a way of subverting what ought to be. You know what would happen in one series of events. Yo may be able to prevent it happening in another.
Your emotions rule you, a ruler does not need that.