We have been talking about this new model for a few days first from early rumors you heard here on Faeit 212, to While Dwarf leaks from over on La Voz de Horus, to now.... the official announcement of the model.
If you still don't know who this is.... There is a link below to details on this Black Library character.
Previously on Faeit 212
via the Warhammer Community
To learn more about Gregor Eisenhorn, head to the 40k wiki