This patch allows players to participate in a special event called “The Darkening of Tristram.” In said event, players can explore a recreation of the original “Diablo” game’s cathedral – complete with its 16 dungeon levels, bosses, monsters, and events.
To make the experience as retro as possible, a “RetroVision” filter gives the cathedral grainy, pixelated visuals, while the music and sound effects are taken from the original game. Additionally, while players are free to use “Diablo III’s” character classes, each class is limited to 8 directions of movement.
Blizzard Entertainment also created a “Diablo” 20th Anniversary site, which boasts videos, developer insights, and a discussion about the game’s history.
The “Diablo” 20th Anniversary celebration extends across Blizzard’s other titles. The new features are detailed here.
Lastly, head to this link to check out the “Diablo III” anniversary sale.
SOURCE: GMA