It's been in continuous development for a long time (fell out of my radar), and it seems like it's in a great shape now.
The mod requires both of Grim Dawn's expansions, and here's the installation guide:
forums.crateentertainment.com
Check out the full information here:Reign of Terror is a full remake (not a 1:1 copy) of the classic ARPG Diablo II, and includes all content and classes present in the original Diablo II, including its expansion, Lord of Destruction. It uses all the original sounds and music, and even all the cut scenes available in-game. In addition to this, as this is a Grim Dawn mod, it also features all Grim Dawn Classes and items, and all of the core mechanics of Grim Dawn.
Since the core mechanics cannot be changed, a perfect Diablo II replica is not possible. This is as close as it can be however.
The mod requires both of Grim Dawn's expansions, and here's the installation guide:

[Mod] Reign of Terror
Current version: 0.7.6.3 Mod inspired by Diablo 1 and Diablo 2: Lord of Destruction Compatibility: Grim Dawn Forgotten Gods expansion (requirement: base Grim Dawn, AoM and FG xpacks) RoT-Wikipedia: Make sure to re-import RoT database after mod update when using GD Stash...
