MultibandDistortion is just what you’d think- instead of just highpassing the signal, it splits it, and distorts each band separately, and recombines them in a strange matrix with a stability control. Separate hardness controls on each band, very flexible.
This is one of those plugins where I don’t think there’s really a correct way to use it. There are many knobs. Fool with them. It’s very much not a ‘dial in tonal purity’ plugin, it’s a ‘wreck stuff’ plugin so experiment and see what you can get out of it.