Complex sentence: Twelve qualifying teams from around the world participated in the championship, which boasted the largest prize pool in the history of e-sports tournaments at the time at 2 million, 1 million going to the champions, until The International 2013 beat it the next year.
Split into simpler sentences: Twelve qualifying teams from around the world participated in the championship, which boasted the largest prize pool in the history of e-sports tournaments at the time at 2 million, with 1 million going to the champions. The tournament total $2 million USD prize pool was the largest until The International 2013 beat it the next year.