During the ancient times, there were magical beasts, which fed not on plants nor meat, but only on thunderbolts. All of these thunderbolts, once ingested, then gathered in the hearts of these beasts. After the bests accumulated layers upon layers of the thunderbolts, eventually the thunderbolts would condense into a daunting energy.
The beasts were gentle by nature, never hurting anyone. But, when they got provoked or backed into a corner, they would cause their hearts to self-destruct. Rumor has it that if a Thunder-Devouring Beast, who had been around for many years, blasted its own heart away, the impact from that self-destruction would be inestimable!
There was another rumor about an Earthly Sovereign, who tried to capture one of the beasts and keep it as a pet. But the creature was so furious that it exploded its own heart. In the end, the Earthly Sovereign died in the explosion.
