Not mud....
But Divine Divinity.
Made by the same people {Larian Studios} that made Divinity Original Sin was released circa 2002.
http://store.steampowered.com/app/214170/
It has the open world feeling of a Elder Scrolls game, the combat of Diablo and the writing/quests from Arcanum or Planetscape Torment. Spring for the whole 1.19 and ye will not be disappointed. I promise.
+1 A very good rpg!