You gain the ability to meditate deeply, remaining semiconscious for 4 hours instead of sleep, After resting in this way, you gain the same benefit that a human does from 8 hours of sleep.
Dark Channel Divinity
Starting at 2nd level, you choose your Dark Channel Divinity:
Dark Channel Divinity: Aura of Shadow
Starting at 2nd level, you can use your Channel Divinity to create a field of warding shadows.
once per short rest, as an action, you can cause swirling darkness to coalesce in a 10-foot radius originating from you. The aura moves with you. When you create the aura, you can designate a number of creatures up to half your cleric rounded down, that you can see, that gain the ability to see through the magical darkness as if it weren’t there. The chosen creatures don't gain the aura’s effects.
Creatures in the aura have disadvantage on all attack rolls, you gain resistance to radiant, and ranged attacks made against you have disadvantage. The aura lasts for 1 minute or unless you are knocked Unconscious.
Dark Channel Divinity: Avatar of Shadow
Starting at 2nd level, you can use your Channel Divinity to mold nearby shadows into a being of pure semi-solid darkness.
As an action, you present your holy symbol and summon an Avatar of Shadow in darkness. The Avatar of Shadow is under your complete control and acts after you in initiative, and you may command it freely using a mental connection.
The avatar remains until it is destroyed, until the following dawn, or you finish a Long or Short rest.
If you use this feature again, each previously created Avatar of Shadow is destroyed. At 8th level, you are able to have 2 Avatar of Shadow
Avatar of Shadow
medium construct, unaligned
Armor Class: 10 + half your cleric level(rounded up)
Hit Points: 10 + three times your cleric level
Speed: fly 30 ft(hover)
STR, DEX, CON, INT, WIS, CHA: 1 (-5).
Saving Throws: STR, DEX, CON +0, INT, WIS, CHA + Spellcasting Ability Modifier
Senses:Darkvision 60 ft. Passive Perception 10 + Spellcasting Ability Modifier
Languages: All languages known to you.
Traits
Incorporeal Movement. The avatar can move through other creatures and objects as if they were difficult terrain. It takes 4(1d10) force damage if it ends its turn inside an object.
Actions
Touch of Shadow.Melee weapon attack: Your spellcasting to hit modifier, reach 5 feet., one target. Hit:(1d8 + Spellcasting Ability) necrotic damage.
Dark Channel Divinity: Shadow of the Dusk
Starting at 2nd level, you can use your Channel Divinity to harness darkness, destroying light and dealing necrotic damage to your foes.
As an action, you present your holy symbol, and create a flash of magical darkness in an aura around you. Any Light within 30 feet of you is dispelled. Additionally, each hostile creature within 30 feet of you makes a Constitution saving throw. A creature takes necrotic damage equal to 2d10 + your cleric level on a failed saving throw, and half as much damage on a successful one.
Shadow Step
At 6th level, you gain the ability to step from one shadow into another. Once per short rest, when you are in dim light or darkness, as a bonus action you can teleport up to 60 feet to an unoccupied space you can see that is also in dim light or darkness
Death Defiance
At 8th level, you have become one with dark energy and you are able to use it to twist your fate. Once per short, When you are knocked down to 0 HP, you can use your reaction to deal 1d8 Necrotic damage to the attacker, and gain that many HP back.
The damage increases to 2d8 at 14th level, and the number of uses increases to 2 at 14th level
Divine Darkness
Starting at 17th level, your dark energy is becoming more powerful you can generate your own darkness. You choose your Divine Darkness:
Light Well
Starting at 17th level, your dark arts become so powerful you can generate your own darkness. You gain resistance to Necrotic Damage and Poison Damage.
As an action, you can suck the light out of the area around you, creating a 30 ft radius sphere of pure darkness and 30 ft of dim light. You may designate up to a number of creatures equal to half of your cleric level rounded down, within 60 feet of you that you can see, that will be able to see through the darkness. Those creatures gain resistance to Necrotic Damage and Poison Damage, while within the darkness. Only a light spell of 6th level or higher can penetrate the darkness. Avatars of Shadow have advantage on attack rolls inside the darkness and dim light area.
Once you use this feature, you can't use it again until you finish a long rest
You can move through other creatures and objects as if they were difficult terrain. You take 2d8 Force Damage if you end your turn inside an object. When you hit with a ranged attack, the target must make a CON saving throw against your spell save DC, on a fail, the creature takes 2d8 + your Wisdom modifier Necrotic Damage. On a save, the creature takes half damage. You can remain in this form for up to 1 minute.
Once you use this feature, you can't use it again until you finish a long rest
Visage of Darkness
Starting at 17th level, you can use your action to activate an aura of magical darkness that lasts for 1 minute or until you dismiss it using an action. Darkness surrounds you in a 30 ft radius. Any hostile creatures in the darkness have disadvantage saving throws, attack throws, and any ranged attacks made into the darkness also have disadvantage. When a hostile creature starts their turn in the darkness, takes 2d8 Necrotic Damage
Once you use this feature, you can't use it again until you finish a long rest
By the time I got to Dark Channel Abilities, I was already thinking this Subclass was going to be overpowered.
The abilities are extremely potent and I would have a hard time not taking a 2 level dip for just about any other class.
Magical Darkness, semi-permanent summoning, teleportation, Once per short rest combo attack/revival/healing, 1 minute of Etherealness..., etc
The Spell list also takes heavily from Warlock exclusive* options.
This subclass is basically a buffet of greatest hits.
I would recommend going back through with a different color and putting in what you used as a reference for the balance of each feature. Also, consider where it falls in the power hierarchy of the other Domains.
I have been work on this subclass, and I took a lot of inspiration from some other subclasses I found, and I want feedback:
NOTE: Most of this is from other subclasses, with some adjustments, and I will not be posting this publicly.
Eyes of the Night
When you choose this domain at 1st level, you can see normally in all darkness, magical or nonmagical, to a range of 120 feet
Domain Spells
You gain domain spells at the cleric levels listed in the Dark Domain Spells table. See the Divine Domain class feature for how domain spells work.
Dark Domain Spells
Passage of Night
You gain the ability to meditate deeply, remaining semiconscious for 4 hours instead of sleep, After resting in this way, you gain the same benefit that a human does from 8 hours of sleep.
Dark Channel Divinity
Starting at 2nd level, you choose your Dark Channel Divinity:
Dark Channel Divinity: Aura of Shadow
Starting at 2nd level, you can use your Channel Divinity to create a field of warding shadows.
once per short rest, as an action, you can cause swirling darkness to coalesce in a 10-foot radius originating from you. The aura moves with you. When you create the aura, you can designate a number of creatures up to half your cleric rounded down, that you can see, that gain the ability to see through the magical darkness as if it weren’t there. The chosen creatures don't gain the aura’s effects.
Creatures in the aura have disadvantage on all attack rolls, you gain resistance to radiant, and ranged attacks made against you have disadvantage. The aura lasts for 1 minute or unless you are knocked Unconscious.
Dark Channel Divinity: Avatar of Shadow
Starting at 2nd level, you can use your Channel Divinity to mold nearby shadows into a being of pure semi-solid darkness.
As an action, you present your holy symbol and summon an Avatar of Shadow in darkness. The Avatar of Shadow is under your complete control and acts after you in initiative, and you may command it freely using a mental connection.
Traits
Actions
Dark Channel Divinity: Shadow of the Dusk
Starting at 2nd level, you can use your Channel Divinity to harness darkness, destroying light and dealing necrotic damage to your foes.
As an action, you present your holy symbol, and create a flash of magical darkness in an aura around you. Any Light within 30 feet of you is dispelled. Additionally, each hostile creature within 30 feet of you makes a Constitution saving throw. A creature takes necrotic damage equal to 2d10 + your cleric level on a failed saving throw, and half as much damage on a successful one.
Shadow Step
At 6th level, you gain the ability to step from one shadow into another. Once per short rest, when you are in dim light or darkness, as a bonus action you can teleport up to 60 feet to an unoccupied space you can see that is also in dim light or darkness
Death Defiance
At 8th level, you have become one with dark energy and you are able to use it to twist your fate. Once per short, When you are knocked down to 0 HP, you can use your reaction to deal 1d8 Necrotic damage to the attacker, and gain that many HP back.
The damage increases to 2d8 at 14th level, and the number of uses increases to 2 at 14th level
Divine Darkness
Light Well
Shadow Form
Your shadows become strongers and your form can become twisted into them. You gain the ability to transform yourself into a shadow. As a bonus action, to can transform into a shadow, you gain have immunity to Poison Damage and Necrotic Damage. You are vulnerable to Radiant Damage, and you are resistant to all other damage types except Psychic Damage and Force Damage. You are immune to being grappled, paralyzed, petrified, poisoned, prone, and restrained.
You can move through other creatures and objects as if they were difficult terrain. You take 2d8 Force Damage if you end your turn inside an object. When you hit with a ranged attack, the target must make a CON saving throw against your spell save DC, on a fail, the creature takes 2d8 + your Wisdom modifier Necrotic Damage. On a save, the creature takes half damage. You can remain in this form for up to 1 minute.
Once you use this feature, you can't use it again until you finish a long rest
Visage of Darkness
Starting at 17th level, you can use your action to activate an aura of magical darkness that lasts for 1 minute or until you dismiss it using an action. Darkness surrounds you in a 30 ft radius. Any hostile creatures in the darkness have disadvantage saving throws, attack throws, and any ranged attacks made into the darkness also have disadvantage. When a hostile creature starts their turn in the darkness, takes 2d8 Necrotic Damage
Once you use this feature, you can't use it again until you finish a long rest
By the time I got to Dark Channel Abilities, I was already thinking this Subclass was going to be overpowered.
The abilities are extremely potent and I would have a hard time not taking a 2 level dip for just about any other class.
Magical Darkness, semi-permanent summoning, teleportation, Once per short rest combo attack/revival/healing, 1 minute of Etherealness..., etc
The Spell list also takes heavily from Warlock exclusive* options.
This subclass is basically a buffet of greatest hits.
I would recommend going back through with a different color and putting in what you used as a reference for the balance of each feature. Also, consider where it falls in the power hierarchy of the other Domains.