After we got to fight tougher versions of the Gaping Jaw, Darkdrift Knight, and Sentient Pest in Elden Ring: Nightreign, we knew that FromSoftware wasn't going to leave the other bosses out of the equation.
Tricephalos, Augur, Equilibrious Beast and Fissure in the Fog are getting buffed-up forms on the 31st of July, rounding out all of the main bosses in the game with new, extra-hard fights besides the Nightlord himself.
There's no word on how the bosses will be made harder to fight, nor in what order they'll be arriving in. As was the case last time, it's likely that this Everdark cycle will involve one boss, then another, and another until we've fought them all, only to then see them come back for a brief period in rotation.
After this batch of Everdark Sovereigns, there's hope all of the tougher bosses will just be added to the game. Once that's done, we'll have to see what other challenges FromSoftware has cooking.