Faster compression & Imperial Camp boxes

what are BC and WC?

That would be Beyond Chaos and Worlds Collide, the two most popular randomizers in all the land, BC being the most insane (in a good way) of the two, with tons of randomized sprites, songs, skills, and pretty much everything at this point, while WC is more vanilla-feeling-experience, but is an "open worlds" type format, so the treasures and bosses are all randomized, which makes for an excellent race setting. I think WC is now also doing the tons of randomized sprites as an option - there's lots of options for both to customize the randomness to your liking etc.