Probably Orcus, as your god.
The Death Domain is an official domain but that's not the version they ended up using. In the GM's Guide on page 96 it lists
1st: False Life, Ray of Sickness.
3rd: Blindness/Deafness, Ray of enfeeblement
5th: Animate Dead, Vampiric Touch
7th: Blight, Death Ward
9th: Antilife Shell, Cloudkill
Bonus Proficiency: When Clerics chooses this domain at 1st level, they gain proficiency with martial weapons.
Reaper: at 2st level, the cleric learns one necromancy cantrip of his or her choice from any spell list. When the cleric casts a necromancy cantrip that normally targets only one creature, the spell can instead target two creatures within range and within 5 feet of each other.
Channel Divinity: Touch of Death. Starting at 2nd level, the cleric can use Channel Divinity to destroy another creature's life force by touch. When the cleric hits a creature with a melee attack, the cleric can use Channel Divinity to deal extra Necrotic Damage to the target. The extra damage equals 5 + 2xCleric Level
Inescapable Destruction: Starting at 6th level, the Cleric's ability to channel negative energy becomes more potent. Necrotic Damage dealt by the character's cleric spells and Channel Divinity options ignore resistance to Necrotic Damage.
Divine Strike: At 8th level, the Cleric gains the ability to infuse his or her weapon strikes with necrotic energy. Once on each of the Clerics terns when he or she hits a creature with a weapon attack, the cleric can cause the attack to deal an extra 1d8 necrotic damage to the target. This increases to 2d8 at 14th level.
Improved Reaper: Starting at 17th level, when the Cleric casts a Necromancy Spell of 1st through 5th level, that targets only one creature, the spell can instead target two creatures within range and within 5 feet of each other. If the spell consumes its material components, the cleric must provide them for each target.