Ive been playing this game for about 3 years now on and off and i have yet to see a legendary brawler come from a mega box let alone big brawl box or brawl box, i can however say that i have pulled one mythic and it came from a regular brawl box so dont get discouraged with how long it takes you to unlock new brawlers and level up on power points, i just got my first power 10 brawler last month and have 2 more chromatic brawlers to unlock, (Gale and Belle) no legendarys though