Grim Dawn also has a mod called Reign Of Terror that lets you play the entirety of Diablo 2 in GD, complete with classes, skills and items! It has some differences because it's built on Grim Dawn's systems, so it has the dual-class system from Grim Dawn (with similarly laid out skill trees), item affixes work like Grim Dawn, etc, but it feel great to play! And you can combine Grim Dawn classes with D2 classes, D2 classes with other D2 classes, or just play the D2 campaign with a regular Grim Dawn build. It's great!