In all the worlds in the mutliverse, evil exists, simply because it must. For without evil, there is no good. For without evil, there is nothing to fight, nothing to resist, nothing to overcome.
In some of the universes, evil is nothing more than a slight imperfection, a minor flaw in an otherwise "perfect" picture. In others it is everything and everywhere, except for the tiniest glimmer of light in an otherwise dark universe.
In all of them, true evil knows one thing: That Evil exists only because it must. That no matter what happens, they can not win, however they also can not completely lose.
So those who know do the evil that they do, knowing that are taking a necessary role in the universe, they are a pivotal point in existence, the exist as a foundation stone for reality. And most of all, they don't take it all that seriously.
For this is how the Friday Night Poker Club started. A great evil extended it's influence to the far reaches of it's universe, and discovered that the walls between were not completely solid, and, while no travel between could be achieved, communications could occur.
So one great evil found another, and they in turn found another, and then a third, and a fourth, and so on. Until eventually the group was formed as a kind of trans-universal pen pal collective. All the supreme evil in their own universe, all equals.
Eventually it was discovered that while they had no ability to influence each others realms, they, if they put their minds to it, could create a shared realm. In this shared realm they all could manifest, and influence their shared reality. It was then that someone introduced the concept of poker...
And so it came that eight of the most evil beings in all the multiverse, spent one night a week playing poker. With souls as the currency, of course.