World buffs in WoW Forever are meant for the open world only: they don't work in dungeons, raids or battlegrounds. That comes from an interview with game director Ion Hazzikostas, reported by MeinMMO in September, where he said there'd be no world buff farming for raids. Blizzard hasn't put it in patch notes or a blue post, and players asking on the forums haven't had a staff answer.
Why it matters
In Classic, raiders spent hours collecting world buffs before every raid. If Forever turns them off inside instances, that stops being part of raid night. Raids in Forever are also smaller and open on 9 December, see raid release dates.
Traces of Silithyst
Reported: Traces of Silithyst exists in Forever. You get it by handing in Silithyst in Silithus, and players describe it as 5% more damage for 30 minutes with no healing bonus. That it doesn't work in raids comes from reports of the BlizzCon demo, not from Blizzard. See how to get to Silithus.
The Classic buffs
Rallying Cry of the Dragonslayer, Songflower Serenade, Warchief's Blessing, Spirit of Zandalar and the rest are listed on some fan sites, but mostly from Classic data. We haven't seen any of them confirmed for Forever, and the Onyxia and Nefarian head turn-ins depend on raids that aren't open yet. The Darkmoon Faire's Sayge fortunes are the one buff of this kind you can get this week.
What Forever has instead
- Camp buffs. Campfire buffs last an hour and copy class buffs, without stacking with them, Blizzard said in its panel recap. See the camping system.
- Legacy perks. Permanence makes party, raid and camp buffs last longer, and Gourmand does the same for food. See the Legacy system.