Harvest Festival

The Harvest Festival (魔王ヘの進化) occurs once all the requirements for the evolution to a True Demon Lord are met. Once it is about to begin, the Voice of the World will announce it and it will start immediately and cannot be stopped even by the one undergoing the evolution.

During the Harvest Festival, the one ascending undergoes a transformation in which they can physically and racially evolve, and gain a tremendous amount of Magicules though the exact amount may vary depending on the individual. It is easier to gain new or evolve existing Skills during the transformation. There is also the potential risk of a significant change in personality. Additionally, the subordinates of the one who ascends will also receive "gifts" of power or ability.

Known Harvest Festival

 * Guy Crimson's Harvest Festival. The end result of a nation foolish enough to summon him, Guy slaughtered both sides, ensuring his awakening.
 * Milim Nava's Harvest Festival. After the murder of her pet dragon, Milim proceeded to rampage in a manner surpassing anything Veldora had ever done, slaughtering the nation and destroying everything in range, only to be stalemated by Guy and Ramaris at her full power for the weeks needed for her to think clearly again. By the time her consciousness had returned, she had already fulfilled the criteria to become a true demon lord.
 * Rimuru Tempest's Harvest Festival. Rimuru evolved and awakened into a True Demon Lord through using the 10,000 Souls of the invading Farmus Army. The process involved the revival of Tempest citizens including Shion, that were killed by the Kingdom of Falmuth's Otherworlders previously. Everyone connected to Rimuru via Soul Corridors received "gifts" which included Skills and species evolutions.