Spesifically "Magical Multitudes" verse and little Tho'at blobs that start to spawn in cycles after cycle 4.
When there are a lot of mobs on the screen channeling their skills along with Tho'at blobs it lags the game so heavy i can't break free properly like in prime hour Cyro.
And Magical multitudes always cause lag regardless if there are other mobs doing things or not.
I am playing the game on fairly low settings. Shadows turned off, max particle effects on screen restricted etc.