These knights belong to a group of (four) apparitions, which Mirror Images can turn into.
It only drops a Bag You Desire for players with at least one of Goshnar's Taints. The more taints you have, the higher the chance. The Bag is always dropped inside a Reward Container so there's no risk of leaving it behind in the creature's corpse.
Damage Taken From Elements
This creature fights in close range. A knight's apparition never retreats.
It didn't walk over Fire Fields until March 09, 2021, when this behavior was changed.
Its experience was reduced from 28,600 to 21,450 and its loot in 16% with the balancing changes on April 15, 2021.