World of Warcraft will finally allow fans of both sides to play together in Patch 9.2.5 after years of having a faction barrier. While most instances will be available for Alliance and Horde to cooperate, there are some raids and dungeons that will not feature cross-faction play when the feature launches. These outliers contain story points or bosses that are unique to each faction, and so creating a way to implement both Alliance and Horde into the instance together was not feasible for Blizzard to get ready in time for launch.
Raids that will not have cross-faction play are Trial of the Crusader, Vault of Archavon, Icecrown Citadel, Baradin Hold, and Battle of Dazar’alor. Trial of the Crusader specifically features unique main characters in the audience that are important to the story of the raid. Icecrown Citadel has an entire fight that takes place on either a Horde or Alliance gunship based on faction. Battle of Dazar’alor is probably the most faction-specific PvE content in the game currently as there are several bosses unique to each faction as well as a mechanic that switches your faction halfway through the raid to show you the other side’s perspective.
In terms of dungeons, Trial of the Champion and Darkmaul Citadel will not feature cross-faction play at launch. Trial of the Champion is similar to its raid counterpart where several things change based on whether you are Horde or Alliance, and Darkmaul Citadel is the Exile’s Reach starter dungeon that has different NPCs accompanying you based on your faction choice.
Content will only be available for cross-faction play through the premade group-finder, and not by using the dungeon finder or raid finder queue system. Players must also toggle the ability to accept both factions before listing the group, and can opt-out if they so desire.
