Just a redesign of the Warden from Minecraft, or rather the one from the Deep Dark. As its name suggests, its purpose is to keep the sculk, but also a keeper of souls, and there are many Wardens lurking in the Deep Dark, waiting to be summoned by a shrieker (after it shrieks 2-6 times in a row, dependent on difficulty) . Each Warden is connected to the sculk hive-mind and appear to be acting as the "Head", being capable of controlling the Sculk infested whenever it is let loose, and acts as a "boss" of sorts towards the other Sculk mobs. It is feared among those who mine in the deeper caves, and many who encounter it do not survive. Perhaps as a result of being adapted to the dark and underground conditions, Wardens are blind with their "Eye" being their mouths, and rely on their senses of hearing, touch, heat detection, and smell to navigate around.
If one wants to avoid getting caught by a Warden, throwing a ball in its direction will be enough to distract it, that is if the Warden noticed you enough yet. Good lucking trying to fight it- as Wardens have the highest melee damage of any mob, has the ability to infect others with its bite (although rather rare compared to the other "spreader" sculk mobs), and a sonic boom should you try to pillar up. It is additionally speculated that Wardens are from the Otherside, a mysterious dimension that acts as a flipside world to the Overworld and Nether, and lacks natural light. Though this is unconfirmed outside of reports of a central portal structure in the ruins of Atoun City-there is just as much evidence as there is for it being portal as there are against it being one.