Barry thought that what he was doing now was the best decision. Even if it meant he had to cooperate with the enemy.
No one knew what would happen later when Destruction decided to unleash more of his power to destroy them. They didn't know how far the limits of his abilities could extend.
So Barry thought it was better to find a way to defeat him as quickly as possible. If there were risks involved, then he just had to bear those risks as he always did.
Suddenly, Aeon's body moved again like before. His desire for killing and destruction became evident once more. He struck at Barry, who was closest to him.
Then the others joined the fray, adding to the chaos of the battle.
But it was just a repetition. Barry didn't see any changes and began to think that perhaps what had happened earlier meant nothing, just a deception, or maybe the real Elf trapped inside his own body couldn't do anything to fight against the power of Destruction.