Blackjack is a snake obsessed with gambling. As long as he sees it as a fair bet (on his end), he'll wager just about anything. Being infamous on the underground gambling scene, he's a popular target for new players wanting to show they belong. As long as they have something he wants, he'll accept challenges from new faces. However, when he says winner takes all, he means it literally.
Blackjack is capable of shifting into a rubber state and absorbing those wrapped in his coils, gaining some of their knowledge in the process. Though he's picky about who he takes in, those who are are in for a lifetime of sitting in the passenger's seat of Blackjack's body. They'll be able to see what he sees and feel what he feels, but will never be able to move on their own. After many years of their minds being stuck inside him, their bodies long gone, his victims usually end up forgetting that they were anything but part of a being greater than them.
Of course, Blackjack doesn't let them go once he has them. Their minds are ripe with strategies that could help him in various situations after all.
Those he doesn't absorb are usually taken to his home and hypnotized into serving him, either personally or as an "employee" in his casino.
He's not void of honor though. If an opponent beats him, he holds up his end of the deal they agreed to.