The workhorse instruments of the 8-10m class observatories are their multi-object spectrographs (MOS), providing comprehensive follow-up to ground-based and space-borne imaging. With the advent of deeper imaging surveys from, e.g., HST, VISTA, JWST and Euclid, there will be a plethora of targets for E-ELT spectroscopy. We believe there is a strong and compelling case for a MOS as one of the first E-ELT instruments. By exploiting the excellent image quality across the full focal plane of the telescope, combined with its tremendous light-gathering power, we will be able to obtain the large samples necessary to tackle some of the key scientific drivers of the E-ELT project, ranging from studies of stellar populations out to the highest-redshift galaxies.