It's basically a saturation / distortion device, that can be configured as serial, parallel and multi-band, with each of the modules having its own transfer curve - chosen from quite a list of typical and unusual shapes - followed by interesting filters, all fed into a feedback unit, topped up with a super-comprehensive modulation matrix.
All of this together results in a huge range of applications: from gentle mastering saturation, to heavy shaping and violent distortions:
----------------
The closest thing I've found in RE shop is Enforcer Dynamic Saturator, but it's a poor, very limited "replacement" with acquired-taste GUI and confusing workflow. And hasn't been updated in ages.
Any takers?