[RPG] What are the mechanical implications of a Grave Cleric using a slain ally’s essence

balancecharacter-deathclericdnd-5e

On page 20 of Xanathar's Guide to Everything, the Grave Cleric's Keeper of Souls ability is detailed.

Starting at 17th level, you can seize a trace of vitality
from a parting soul and use it to heal the living. When
an enemy you can see dies within 60 feet of you, you or one creature of your choice that is within 60 feet of you
regains hit points equal to the enemy’s number of Hit
Dice

Emphasis mine. I was curious why it specifically outlines slain enemies instead of slain creatures. My initial thought was that without that specific wording you could in theory just keep resurrecting a slain ally by giving him hitpoints back to himself after he died, and that it was written that way to prevent only that case. I do not want to heal an ally with his own essence, but rather a different ally. Rules as written, my judgement says you cannot use a slain ally's essence. But, I want to know if the balance of the game would be significantly upset if one allowed a slain ally's (or non-enemy's) essence to be used on a different ally or oneself. Am I creating any loopholes that could bite me in the butt later? Does healing from any creature's death make the Grave Cleric too powerful or versatile?

Since enemies and allies aren't really defined, I want to be prepared in the event that myself or a player wants to test the bounds of the rules by considering a slain ally as an enemy for the purposes of healing another.

Best Answer

Per the SRD:

A creature that has died can't regain hit points until magic such as the revivify spell has restored it to life.

So you cannot heal a dead comrade by stealing their dead essence.

The above answers the core question, about using a character's own death to resurrect them. The rest seems to be asking for opinion which I thought was frowned upon. But here goes...

No, I don't see a great upset in the balance. This spell is more of a "topping up" heal than granting any great boon. Considering the cleric must be at least 17th level to cast, we can assume that their allies are also 17th level, which means the spell will only heal for 17hp. Whereas at 17th level the cleric has access to the 6th-level spell, Heal:

Choose a creature that you can see within range. A surge of positive energy washes through the creature, causing it to regain 70 hit points. This spell also ends blindness, deafness, and any diseases affecting the target. This spell has no effect on constructs or undead. At Higher Levels. When you cast this spell using a spell slot of 7th level or higher, the amount of healing increases by 10 for each slot level above 6th.

Most other humans the character is likely to meet (and be an ally) would have less than 5 Hit Dice. Which might be enough to bring back another player from the brink of death, but at what cost? Will the cleric kill off a village just to fully heal the party?

The only advantage this has is that instead of one big burst of healing, the cleric can give out a little here and there (depending on how often the cleric is allowed to use the skill per day).