Their argument is cut short when they are attacked; Korrina rushes off to apprehend the perpetrator, but Gurkinn remains. Essentia appears and questions him about Mega Evolution. After a brief conversation, Gurkinn realizes the danger she presents, and he and Korrina destroy the Tower of Mastery to prevent her from possessing its secrets, including the secrets of a special Pokémon.
Gurkinn is a good-natured if slightly sly old man who is not afraid to take a hit from his granddaughter. He is also decisive enough to destroy his treasured Tower of Mastery when he realizes it is in danger of being misused.
Heracross underwent Mega Evolution during his battle with Essentia. Mega Heracross and Korrina's Mega Lucario later worked together to trigger the self-destruct of the Tower of Mastery.
Korrina and Gurkinn seem very close. Korrina will hit Gurkinn if she is really frustrated, and Gurkinn only takes it in stride with a bit of whining. Korrina also follows Gurkinn's instructions even when she doesn't understand them, even when they necessitate something as drastic as destroying the Tower of Mastery.