Sounds like Kaijudo: Rise of the Duel Masters (2012-2013).
Kaijudo is a 2012 American animated series and trading card game that serve as a spin-off and relaunch of the Japanese Duel Masters franchise. The animated series was produced by Hasbro Studios, animated by Moi Animation in South Korea, and developed by Henry Gilroy and Andrew R. Robinson for Wizards of the Coast.
The series follows the adventures of a young boy named Ray Okamoto from San Campion who possesses the rare ability to summon and duel alongside fantastical creatures from a parallel dimension. Ray and his two best friends Allie and Gabe join the ranks of the mysterious Duel Masters to ensure the survival of both races.
The main character, Ray, has mostly-black hair, and can summon a creature called Tatsurion the Unchained, a quadrupedal fire beast with horns and a tail. There's also a blonde girl, Allie, and another boy, Gabe, who can summon creatures of their own.
The light master you referred to might be Master Nigel Brightmore, a former Duel Master himself, and "an expert on the Light Civilization and its creatures," who ended up siding with The Choten, another former Duel Master, and the chief antagonist of the series.