Above is the Blood of Oryx variant of the Hive Knight. The Knight's been reskinned a lot more than other Hive, so there are a lot of variants here.
Hidden Swarm:
Spawn of Crota
Venom of Oryx
The Silent Brood:
Generic
Sardok, Eye of Oryx
Vorlog
Ecthar, Sword of Oryx
Vessel of Oryx

A roaring, striding fortress, the Knight is the Hive's foremost and most
zealous defender. Centuries of battle have toughened the bony
protrusions on its body into an armor as hard as relic iron - a defense
only strengthened by the Hive magic that Knights use to summon shields
of burning force.

Source:http://db.destinytracker.com/grimoire/enemies/hive/knight

UPDATE 1/11/22 - Updated Ecthar to be grey to accurately match his in-game counterpart as well as updating the Venom of Oryx variant

UPDATE 6/30/22 - Added Generic variant

UPDATE 8/16/22 - Darkened skin for Generic variant

UPDATE 6/5/23 - Updated eyes and helmet