I love tumblr. It is a wonderful place to grab ideas. I stumbled upon this:
Amazing. Absolutely amazing. Just looking at the creature, a dozen traits come to mind...
Servators of the Old Empire
Whatever happened to the Old Empire is lost in mystery. One day, the borders closed and never reopened. Trade diminished, and the realm slowly fell into darkness. Accounts from those who escaped tell of the population slowly becoming twisted and evil.
The only official contact with the Old Empire is through the Iron Bishops that act as diplomats and negotiators. The Old Empire hungers for metals, magic items, and gems and the Iron Bishops find regions to supply them. They have a way of impressing the needs of the Old Empire on the rulers of the surrounding regions.
Still Human, All Flawed
Iron Bishops still show a reflection of their former humanity and are still technically living. They often travel alone or with a small escort. In combat, they immediately use their "You know nothing" ability to stun as many as their aggressors as possible. They then focus their efforts accordingly with "withering staff" accordingly. Iron Bishops will often focus on the weakest target so they can use their "consume soul" ability.
When I built this creature, I considered using legendary actions, but I wanted a creature that was simpler. The idea behind this creature is that they should be able to stun a large part of the party, which would hopefully allow it to act better in a solo capacity. The "malevolent spikes" and "consume soul" ability allow the creature to heal and dish out damage while not acting.
I haven't playtested the creature yet, so let me know what you think. Download it here.