Horn of the Abyss is a community expansion to the excellent Heroes of Might and Magic III

Horn of the Abyss is an unofficial expansion to Heroes of Might and Magic III and features a whole new race The Cove, gameplay and graphical improvements, new maps and map objects as well as a whole new campaign for you to explore.

And today Horn of the Abyss has gotten even better with further campaign missions, new map objects, bug fixes, graphical improvements, and more. Here's the list of features that come with the Horn of the Abyss expansion:

-New fully playable town – Cove

-New war machine – Cannon. Available at Cove’s Blacksmith

-New artifacts and artifact sets

-New banks and conservatories

-New types of map objects

-New heroes

-Towns change their appearance, depending on Fort level

-Map editor which supports these new features

-Support for bigger map sizes (Huge, XHuge and Giant)

-A lot of balance fixes (finally nerfing the necromancers as well as making life easier for Tower and Inferno)

-A lot of RMG fixes (for example, removing all sea elements from non-sea random maps)

-A lot of graphical fixes (the original game had plenty of graphical bugs)

I haven't personally tried Horn of the Abyss but Heroes of Might and Magic III and its expansions represent some of the best turn based strategy gameplay out there. So a community expansion that doesn't interfere with anything that made Heroes III great while still adding a lot of unique touches and balance fixes to it is more than welcome in my eyes.

I mentioned earlier on that there was a big patch that came for Horn of the Abyss today and it is a bit too big for me to list all of the changes so here are the main features and if you want the full patch notes for version 1.4 you can read them over here.

- Continuation of Horn of the Abyss campaign

- Horn of the Abyss artifact and summoned neutral creature

- 10 new objects as well as various graphical remakes

- Heroes can exchange artifacts and forces in towns 

- Bugfixes and other new features too numerous to list here

If you had an itch to play some Heroes of Might and Magic recently a whole new campaign to explore, as well as new units and map features, are a very convenient excuse to once again reinstall Heroes III.

If you don't own it you can get it dirt cheap during the many currently running sales, though I would avoid the Steam version since its quite pricey while offering less than the GOG one.

Other than that, have fun!