Donatello (2012)

He had found them in the sewer, and study them in secret. It was a short period as he figured out the gems each had a different power. A different god like power, which worked extremely well together. Especially the red one which seems to be power incarnate, the ultimate power source.

He placed them on his belt while hiding them, as he tested their powers. Using them to learn more about them, as well as his world. And even beyond as he could see potential universes, seeing various versions of himself. Including versions which were fighters like Raph, goofballs like Mikey, a leader like Leo, or even something else. He saw himself as other animals, as a human, as an alien, and more.

Then there was the romance angle, as he was the most romantic of his brothers. Not just his crush on April, but on most of the women he met. Karai, Shinigami, Renet, Mona Lisa, and others. Even some harems with them. Even female versions of his allies and his foes.

'So I have the power and ability to do what ever I want? Should I start big and fast or experiment slowly as well as small.?' he thought, organizing the possibilities.