Cave Biomes API would allow quark's various cave "biomes" to become actual functional biomes which would allow for all sorts of future possibilities, and would ensure that cave biomes could spawn in a way that wouldn't mess with those that already use the API. This could also allow for more fine control over the various cave mobs from quark, such as the Toretoises, the Stonelings, and the Forgotten. This could even be an optional dependency, so if for some reason a player doesn't want to use the mod, the quark's caves would continue to generate in the same way they do now.

While a good idea, it's code I'd just be ditching pretty quickly after 1.17 drops soon, so I'll pass.