The guys from the Horus Heresy Campaign mod team have just released a demo version of their mod. What sets this mod apart from others is the fact that it has a single-player campaign. The demo contains the first level.
This is the first mission of the Loyalist Campaign, “Flight of the Eisenstein”, fully playable. It has the new pre-heresy armour for the marines, Captain Garro, and new close combat marines. In its current stage, it does not have models for the two Primarchs featured - Horus and Angron, thus we have models standing in for them, an Obliterator for Horus, and a Force Commander for Angron.
Also, we don’t have voices in place for the cutscenes, so we give you permission to read out the lines in whatever voice you feel appropriate. The final product will include full voice acting.
This Demo contains three difficulty levels, I fully recommend Insane for the full experience of the Horus Heresy.
You can find more information and discuss the demo in this thread. A list of download locations follows below. The team is still looking for mirrors to help with the traffic.