The Altar of Dryzzgor is an object belonging to the Artifact faction. It has slightly less Hit Points than a Lieutenant of the same level, which probably means it's usually a Boss-class object. It has no ranged nor melee attacks, nor it can move.
Unlike many others, this object had no defenders when I found it. And despite the description, it didn't seem like if it was causing any effects on the villains that came close to it. Once I started attacking, no one came to its help, either, and it was destroyed easily.
Be careful, though, of the explosion once you destroy it, which is relatively potent:
This object seems to be regenerating the health of the villains around it.