Age of Doom is a combination of an engine and assets that creates something completely new.
Age of Empires 2 is a great, top-tier video game. Doom is another top-tier, all time success. Modder HELLKNIGHT61 knew these things and used the Age of Empires 2 engine for Doom to become a third-person, isometric RTS… shooter… thing.
HELLKNIGHT61 describes the mod as “I wanted to revive the original DOOM for Age of Empires 2′ game engine.” This was my dream.
The Age of Doom mod for Age of Empires 2 is a campaign that ports ideas, themes, and bits of story from both Doom and Doom 3, sampling audio and enemies from both. It imports sprites and projectiles from the original Doom into Age of Empires 2’s engine. Doomguy is a superhero shotgun-wielding Doomguy, with pinkies and cyberdemons as well as everything you would expect to see. The campaign has four chapters and includes a tutorial. A fifth chapter is still to be published.
To be honest, the whole thing reminded me of Warcraft custom game days. This is something you might try with an RTS engine. HELLKNIGHT61 is the one who has achieved this dream. You can find Age of Doom on ModDB.