So I have a player who wants to play a death domain cleric of Jergal, the lawful neutral god of death.

He has given me a one page backstory that is simple to follow but has, at last count, seven story hooks for me to use. He has talked with me about how he would play this character in combat as a backline debuffer/blaster, for roleplay he has said that his character's whole goal is to simple 'advance the cause of death as Lord Jergal demands'. I asked how he would jell with the party which consists of; a rogue, fighter, paladin, and druid. As his cleric is lawful neutral this shouldn't be a problem, he says, as he would simply join the party since adventures kill a lot of things and 'Lord Jergal doesn't care from wence the death comes only that creature die'. The party gets a divine caster and he gets an excuse to be on the 'good guys' side while reaping the souls of the living.

My question: is there any potential for exploiting this subclass that I should be aware of and what roleplay scenarios might come up that would cause party conflict/pvp?

Quote from Dracis >>

My question: is there any potential for exploiting this subclass that I should be aware of and what roleplay scenarios might come up that would cause party conflict/pvp?

The way to avoid PVP fights is just by banning them at the game and explaining why you don't want them to occur. And handling inter-party conflict shouldn't be too hard if you outline how much/little you want it done, and stress that character conflicts should not turn into player conflicts. Do all this in session 0.

I don't think the subclass features are an issue, they all are focussed on doing more damage in combat and none are overpowered in doing so it all comes dwn the the roleplay.

Allignment is a strange thing that can be interpreted in different ways. when the demands are Lord Jergal conflict with the law of the land they are in how does the character react being lawful. Many peole would killing however I choose because my "god" demands death is Chaotic Evil rather than Lawful Neutral.

What is the PCs reaction going to be with innocent NPCs.  If he goes into town and starts killing innocents the rest of the party are faced with the options of either killing the cleric, handing him in the the law or joining him, turning the game into evil campaign, potentially with the rest of the party no more than the clerics minions. The first two options would require the player to create a new character and the third option creates a campaign that is totally different that what yo envisaged and the whle group (you included) would need ot be happy with that.

What will the cleric go if a PC goes down? The cleric might bring themm back up because they are effective at killing things and therefore there will be more death by raising the PC back up but turning a dead creature into an alive one might be considered aborant to Lord Jergal

What happens when the rest of the party want to avoid killing things. Say the party is tasked with recovering a stolen ring, the rest of the party sneak in to the thieves base, and try to regain it without being seen, or capture the  thieves and take them to the guard. Will the cleric accept the group decision or kill them all regardless of the rest of the party's approach?

Seven story hooks is also a red flag, running a plot hook for each character along with the main story line is a good way to run a campaign, many campaigns have no character hooks and just have the main story and a few sub plots. It might be that the PC is just giving you a number of options if you choose to use character sub plots but it is also possible that he wants to dominate the game.

Sounds reasonable to me. Death Domain is kind of an odd subclass, since it was written to be something more for the DM's use... whether a Cleric gets forcibly changed into one if they start doing evil acts, or if it's just meant to build evil NPCs. It wasn't as carefully balanced as the PHB subclasses released at the same time... but despite all that it's honestly a pretty average Cleric subclass. It's really good at a few specific things. Honestly, the most challenging thing about the subclass is that it gets guaranteed access to Animate Dead, and that's really only challenging because it gives you more creatures to track during combat.

Quote from TransmorpherDDS >>

Sounds reasonable to me. Death Domain is kind of an odd subclass, since it was written to be something more for the DM's use... whether a Cleric gets forcibly changed into one if they start doing evil acts, or if it's just meant to build evil NPCs. It wasn't as carefully balanced as the PHB subclasses released at the same time... but despite all that it's honestly a pretty average Cleric subclass. It's really good at a few specific things. Honestly, the most challenging thing about the subclass is that it gets guaranteed access to Animate Dead, and that's really only challenging because it gives you more creatures to track during combat.

 RAW every cleric has guaranteed access to animate dead as they can prepare it each day. The only difference with death domain is they have permanent access to it.  I agree it can be a problem spell as the caster could have a small army of undead to control while the rest of the group have only one character.

That's a good point. I've never actually seen a cleric take the spell, personally, but it is an option. Still, Death Domain has it permanently prepared once they gain access to it, and I feel like they're more likely to be looking for ways to use it regularly.

I think the way of getting around Animate Dead is quite simply to say that Jergal wants souls; the bodies are of no concernt of him. And maybe that's the leash for potential killing sprees: Jergal, being a bureaucrat, may have a specific list of souls he wants delivered unto him. Depending on where in the lore Jergal is, he could be a begrudging servant of Cyric who is about to face off with Kelemvor, or perhaps Jergal is taking advantage of steering the novice god Kelemvor in the direction which most pleases him. Perhaps Jergal is the only death god, in which case you can make as much up about him as you like. Even then, the Companions of the Pallid Mask can combat and control the undead where they feel necessary, such as running literal skeleton crews to maintain their temples.

I'm reminded of Pathfinder: Kingmaker's Harrim, who worships the god Groetus, who doesn't really need Clerics because He is the god of the inevitable end times. He needs no agents to bring about the end, but Harrim finds peace in following Him. Harrim was Chaotic Neutral though, and his god's domain wasn't necessarily death, but I think his persona fits your character especially if they adhere to Jergal's tenets.

Remember, you are free to adjust the lore however you like — no need to be a slave to the FR wiki. 
If you’re worried about the cleric going all murderhobo, let the player know that in your world, Jergal only wants souls when their time has come, and he’ll be quite upset if the character goes around sending him a lot of early arrivals. Or whatever other kind of guardrails you want to put on it.

Also, I agree that seven plot hooks can be a lot, depending on how in depth they are. It could be a sign of main character syndrome. Make sure the player understands you may not get to all of them.

And a +1 to bard’s points about session 0. Make sure the rest of the players understand what this one is doing. Character conflict can be fun, if it sticks to rp, but player conflict is a game killer. 

It’s totally possible to be a happy-go-lucky chaotic evil necromancer. It’s all about being “party constructive” - no PvP, help the party to do their thing however you can, because - let’s face it - Jergal knows that the greatest force for death in the world is literally any group of DND player characters. Anything that helps these lawful good adventurers is definitely hastening a LOT of deaths, so there’s no need for stress or conflict within the party. Healing and buffing these guys is absolutely appropriate role play for a CE character, and certainly for LN.

I’d suggest as an option, grave domain. Also multiclass Paladin of Jergal for 2 levels, then Grave cleric. This gives you Divine Smite and Path to the Grave for a potential 10d8 smite when, y’know, someone really needs to be embraced by Jergal. Also, Paladin of Jergal is an interesting take on the idea of “Paladin”. :)

i had an order domain cleric once who would, after the party had begun moving on from a looted room, cast Spare the Dying on the unconscious bodies of ne'er-do-wells left behind. the reasoning was so that justice might find them or not as the gods willed. one time that was said even as a grey ooze was creeping over one guy's boot. the gods were not especially cryptic that day about whether nameless thug #3 was going on to greater things.

i'd give this lawful neutral death cleric player a similar cantrip. the player would cast it by passing their hand palm-down across the creatures face. if two ancient (and often relatively worthless) coins appeared on their eyes then the deceased creature's name as well as time and method of death would be magically added to a scroll. the scroll must be returned to the Scriveners of Doom when full or before the last night of every year so that it can be read aloud by the priests. the body is not preserved in any way, but there's something like a DC 15 (Wis) to any attempt to raise or animate the body until the next sundown. the priest is there to take notes, not murder... although this spell might auto-cancel the last death save or two (DM's discretion) because there's always a corners that could be cut for expediency in any bureaucratic undertaking (although the 'lawful' part of 'lawful neutral' might contraindicate that). if no coins appear on the eyes, then the creature is stabilized but remains unconscious. their death will be observed by others or not. if there's no time to stop for cantrips then the cleric will simply jot down a few deaths later and that's equally as good.

a busy vulture doesn't stop to harvest every liver, nor does Jergal's servant stop for every soul's passing.

The are allot of ways to approach the topic of death religiously. Some concepts are better served by domains like twilight  or grave rather than the death domain but the death domain does have it's place. 

Mechanically  and thematically the death domain is the bringer of death and so  implicitly  views death as a good or necessary thing which can be hard to square with good parties. Its your doomsday cults trying to bring on the end of the world, fictional assassin priest hoods and similar evil orders.  For example the attitude of creating death for the sake of creating death  which your player has kind of espoused  can create issues as that's a common villain motivation and will clash with common heroic motivations; it also leans itself to being a bit of a murder hobo which can cause conflict.  It should probably be tempered some how whether its enforcing some kind of fair rules of death, providing solace to the dieing, using death to some other end or negative worship. Really its up to the player to come up with ideas for their character so just say if you wont want a murder hobo or some one too evil and offer some suggestions of how they as a player may avoid that.  Most role play problems can generally be over come as long as people respect basic boundaries and accept the premise that characters must work together and talk it out. 

Here are some ideas of how a death cleric could be run and what I think is the risk of conflict: 

• Angel of mercy/ psychopomp  - This cleric of death provides solace and painless deaths to the sick and dieing.   This is non offensive and shouldn't cause issues. Even if some one is cruel the angel of mercy may get angry but will not necessarily break the party over it. 
• Grim reaper/ assassin for death - This cleric is given a list of people to kill because it's their time, to maintain order, the natural cycle or justice .  Careful with this one as not all players may be on board with a particular character dieing. This may result in mercy kills of certain  unconcious bandits or maybe saving their life as it isn't their time. 
• Death appeaser -  Historically gods were not worshiped the same as Christianity where gods were all seen as objectively good. A cleric  can pray against and try to appease an evil god to prevent some greater wrath.  This is fine as long as the rituals aren't too offensive or everyone is on board.  On the extreme end this may include things like ritual cannibalism or execution/ sacrifice of some prisoners.  Though it may also just be leaving a cake out on halloween, magic is weird. 
• Death cop - maintains the rules of death including specific burial rituals and limiting the use of undeath to only certain situations.  This shouldn't cause issues as long as no one is undead and even if they are that can be resolved by them being a sanctioned undead 
• Seeker of power - This cleric has motivations other than the bringing of death but abides by it's worship for power that they use for some end that could be any alignment.   
• Scholar of death - This cleric studies death and aims to understand it's secrets and may worship a god of death as an avatar of their study.  They may do experiments with death, attempt to commune with the dead or meticulously measure the process.  This shouldn't cause any problems unless some one has paritcular issues with things like summoning undead which this character is likely to do. 

I don't think it is an issue unless the character decides to go on an indiscriminate killing spree which would not fit with their Lawful Neutral alignment.

The subclass itself is reasonably balanced and doesn't require the character to be evil. Death is a part of the cycle of Life. A natural ending to all things.

However, you should perhaps emphasize to the player that Jergal does not seek imminent death for all creatures.Without Life there is no death. Without life, death has no meaning. Without life, Jergal has no followers.

A Lawful Neutral death cleric would be likely to actively preserve the life of creatures who are injured or dying unless the creature in question is upsetting the balance by causing too much Death or the creature is old and likely has no further opportunities to reproduce. A single life preserved can lead to several more lives created which in turn means even more Deaths since Jergal will receive them all in the end. A flourishing society with more births and an increasing population means more death in the long run.

However, reading a bit of the lore. Jergal is mostly a bureaucrat, keeping track of death and the ultimate fate of creatures. Jergal is Lawful Neutral as is the god of Death Kelemvor whom he serves (if your world is using the Forgotten Realms interpretation). So I don't see the choice of a Death cleric for a Lawful Neutral god of death leading to any significant PVP conflicts unless that is what the players want. (P.S. If you don't want PVP conflicts then just say so up front in a session 0 - "I don't mind how much your characters might argue and bicker about philosophy - just remember that the characters know they are on the same team, will help each other and will not come to blows no matter how heated the argument")