World Bosses are evolving in Patch 12.1, retreating from the open world to their own instances, called lairs! They will feature four difficulties, including flex Mythic.
Lairs will be actual raid instances, with four distinct difficulty levels, including flex Mythic! On release, Lairs will be available in the following difficulties: World, Normal, Heroic, Mythic. Mythic lairs will be flex 15 to 25 players, similar to Sporefall.
Lag-Free World
Even if you never complete a single World Boss, the biggest gain from this is the reduction of open-world lag. World Bosses being one of the largest zone-wide lag factors early in the expansion, this change will likely reduce those lag events drastically.
Another Avenue for Player Power
With these changes, we will likely see four distinct World Boss loot lockouts, meaning overall more loot early in the season. With Patch 12.0.7, Heroic World Bosses give Hero track loot, Mythic Lairs will possibly give Myth track loot, entering the radar of every WoW player.
Rotmire, the single boss of Sporefall, is likely a good preview of what to expect from the difficulty of a Lair boss. Rotmire has shown little challenge, even for pugs, but it could be a symptom of fully myth-geared players. Maybe having mythic lair bosses available early in the season could present challenges even for organized groups.
