I think, after a bit of a google, that you're referring to this:

* https://github.com/krimdomu/Rex

I've not sure there's too much overlap, as my initial understanding makes me think that rex carries out scripts over SSH, in a similar fashion to fabric.

I assume that slaughter will be scheduled and will revert changes made manually, for example, it looks like rex will just do its magic at the single point in time you run the script(s).

I'll dig deeper to see if I've misunderstood.