In one corner ... Von Miller, NFL superstar.
In the other corner, Travell "Black Magic" Mazion ... a 13-0 boxer who's a rising star in the sport.
The fight? Von claims he staked Mazion with a $30,000 investment and in exchange, he was supposed to get 20% of all "Black Magic" fight earning.
The problem? Von claims he forked over his initial check in Feb. 2017 -- and hasn't received a dime.
Mazion had a fight in April 2017 -- after Von ponied up his dough -- and expected his cut right away.