Might and Magic: Heroes VI developed by Black Hole Entertainment with use of their own proprietary engine. After Black Hole Entertainment filled bankrupcy, as they failed to convice Ubisoft to finance them over approved budged, the last patches and addons were finished by Limbic Development Entertainment and Virtuos Studio.
This is second attempt, after Heroes V, when Ubisoft aquired Might&Magic license. Similary to Heroes V the game is not much resources demanding, you can download maps and play in-game campaigns. Need to say that not much, there are also not mods, although engine is moddable. That's all because Blackhole wasn't allowed to fine tune the engine and complete it. You also need to play it now without Dynasty System - as it was online only.
Factions: Sanctuary, Haven, Inferno, Stronghold, Necropolis and Dungeon comes with Shades of Darkness Stand-alone expansion.
Reception: The game was accepted well, though there are some gaps in the story (more toward the end) and a few bugs. Overall playability is very good but re-playability is none.