Anub’vir: invisible spikes killing players with a single attack… too much damage, looks like a boss, not a miniboss. And it is usually accompanied by other adds.
Vela and talo hard minibosses too.
He’s actually one of the harder ones but as long as you give yourself plenty of space to maneuver it should be easily doable.
Hmmm I did notice a couple times that the spikes didn’t have swirlies before they popped up. At the time, I thought I must have just not seen them. Maybe it’s bugged, or maybe it’s intentionally been made harder.