Revised: I'm trying to tie in some of the changes recommended by commenters below (with my own flavour, of course).

Revised 27/04/15: Made a few changes to some of the features, particularly the Channel Divinity. In testing seemed a little over powered, but not as much as suspected. Went for a complete revision, but I can recover it to the original if requested. Also clarified the Shadow Guardians spell.

So, I'm trying out my hand at some customisations in 5e and I thought I'd have a go at a domain. I haven't had much chance to playtest this. I've only used it as a Domain for some priests possessed by a shadow being I was using in one of my story arcs. Let me know how you get on if you use it. Is it too powerful/underpowered? Does the motif seem overbearing or have limited usage? Is it something your players want to use?

Shadow Domain

Gods of Darkness, Night, Evil and Death can all grant their followers access to the Domain of Shadow. Often perceived as being gods of trickery, fear, and "dark deeds", gods of this domain can send their followers to spread fear and mistrust, or to protect those whose activities are associated with night and darkness.

SHADOW DOMAIN SPELLS

Cleric Level	Spells
1st	Chill Touch, Blindness/Deafness
3rd	Darkness, Darkvision
5th	Fear, Shadow Guardians (as Spirit Guardians, but the spirits appear as shadows and the damage is cold damage, not radiant or necrotic)
7th	Conjure Shadow Elemental, Shadow Mantle (as Crusaders Mantle, but the damage is cold damage, not Radiant)
9th	Antilife shell, Shadow Walk

Bonus Proficiencies

At 1st level you gain proficiency in and advantage on Dexterity (Stealth) and Charisma (Deception) checks.

Shadow Ward

If you are targeted with an effect that causes necrotic damage, you can use your reaction to gain resistance against the damage and for an additional number of rounds equal to your Wisdom modifier. You may use this feature a number of times equal to your Wisdom modifier (minimum of once). You regain all expended uses when you complete a long rest.

Channel Divinity: Veil of Shadows

Starting at 2nd level, you can use your Channel Divinity to create a "gloom" within 30 feet of you. All enemies within the area must make a Wisdom saving throw against your spell save DC or have disadvantage on their next attack against you. Also, you gain advantage until the effect ends on all attacks against the next enemy within the "gloom" to strike you. The effect lasts for 1 round plus your Wisdom bonus (minimum of 1 round).

Shadow Zone

Beginning at 6th level, you can extend your Shadow Ward out to a radius of 30 feet. All allies within that range gain resistance to necrotic damage for a number of rounds equal to your Wisdom modifier (minimum of 1 round).

Dark Strike

At 8th level you gain the ability to infuse your attacks with the power of shadow. Once on each of your turns when you hit a creature with a weapon attack, you can cause the attack to deal an extra 1d8 necrotic damage. When you reach 14th level, the extra damage increases to 2d8.

The Stuff of Nightmares

Starting at 17th level, you can use your action to activate an aura of shadows that lasts for one minute or until you dismiss it using another action. Each creature of your choice that is within 60 feet of you and must succeed on a Wisdom saving throw against your spell save DC or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature’s saving throw is successful or the effect ends for it, the creature is immune to the fear effect for the next 24 hours. The area is considered heavily obscured, thus everyone within is considered to have concealment from everyone except you.