Note: this subclass is likely not intended as official content: "For the curious, when building stuff for my own campaign I kind of don't care about balance. Anything I can break in design I can counterbreak five times as bad during a session, as needed. Plus, IMO stuff going sideways and weird is why I play the game."—Mike Mearls]
Custom built for clerics of Zehir, and perhaps Lolth.
At each indicated cleric level, you add the listed spells to your spells prepared.
1st level - Arms of hadar, hex
3rd level - Blindness/deafness, darkness
5th level - Fear, vampiric touch
7th level - Blight, Evard's black tentacles
9th level - Contagion, enervation
When you choose this domain at 1st level, you gain the chill touch cantrip. If you do not have darkvision, you gain it with a range of 30 feet.
Starting at 1st level, you can invoke the power of darkness to punish anyone fool enough to harm you. As a reaction when a creature you can see damages you, you cause that creature to become blinded until the end of your next turn.
Once you use this feature, you can't use it again until you complete a short or long rest.
Starting at 2nd level, you can use your Channel Divinity to fade into the darkness.
As a bonus action, you become a creature of darkness that can blend into the shadows. You gain advantage on all Dexterity (Stealth) checks. If a creature cannot see you, your spells and attacks deal maximum damage to them. The shadows seem to draw around, as if they seek to protect you. This benefit lasts for one minute.
Starting at 6th level, your Shield of Ineffable Darkness becomes more powerful. When you use it, you can select up to three additional, hostile creatures you can see within 30 feet of you. They are also blinded until the end of your next turn.
Starting at 8th level, you add your Wisdom modifier to the damage you deal with any cleric cantrip.
Starting at 17th level, you gain strength from darkness. As a bonus action, you fade into the shadows. You regain hit points equal to your cleric level and gain resistance to all damage for one minute. In addition, while this duration lasts you can use a bonus action to teleport up to 30 feet to an unoccupied space you can see that is in dim light or darkness.