Mechiel and Lea did not bring out more of their abilities like Kyros and Listrel because they couldn't.
Their focus was divided as they were trying to harness the power of Charm and the power of the Grendelor.
The march to 'save the lands' was to eliminate the Brimstone curses plaguing the land and causing suffering to the Ygdrassil tree that made up the Planesworld. However, Kyros had the power of the Dryad, and with his numerous Codes and Corruption, he managed to recreate stability in the land.
The Brimstone Beasts had caused an immense change in the climate and were slowly purging the cycle of life. Life and Death energy could not abound, and the cycle was broken as the souls were gathered and held in the beasts' hellish cores.
But when Kyros and the group eliminated nearly ninety percent of the Brimstone Beast in the entire Vey realm, the clouds began to form again.
