I will present a mock stellar catalog, matching in volume, depth and data model the content of the planned Gaia early data release 3 (Gaia EDR3). This catalog (GeDR3mock) was generated using galaxia, a tool to sample stars from an underlying Milky Way (MW) model or from N-body data. It is based on an updated Besancon Galactic model together with the latest PARSEC stellar evolutionary tracks, now also including white dwarfs. Magellanic clouds and realistic open clusters with internal rotation have been added. The uncertainties were empirically modelled based on Gaia DR2 (GDR2) and scaled according to the longer baseline in Gaia EDR3. The apparent magnitudes were reddened according to a new selection of 3D extinction maps. To help with the Gaia selection function all-sky magnitude limit maps in G and BP are included for a few relevant GDR2 subsets. The catalog is available in the Virtual Observatory and can be queried just like the actual Gaia EDR3 will be. I will highlight a few use cases of this new catalog, for example its use as a Galactic prior in parameter estimation and how it can help to approximate the underlying selection function of your sample.