MMORPGs are massive multiplayer online role-playing games that allow players to create characters and adventure in virtual worlds with thousands of other players. The genre originated from single-player computer RPGs and tabletop role-playing games like Dungeons & Dragons. Ultima Online (1997) was one of the first successful MMORPGs. World of Warcraft (2004) became the most popular MMORPG ever due to its expansive world and engaging gameplay, peaking at 12 million subscribers. However, MMORPG subscriber numbers have recently declined with the rise of popular multiplayer shooters like Call of Duty.