The description of guardian of faith (a 4th-level cleric spell) states:
A Large spectral guardian appears and hovers for the duration in an unoccupied space of your choice that you can see within range. […]
Any creature hostile to you that moves to a space within 10 feet of the guardian for the first time on a turn must succeed on a Dexterity saving throw. The creature takes 20 radiant damage on a failed save, or half as much damage on a successful one. The guardian vanishes when it has dealt a total of 60 damage.
And spirit guardians (a 3rd-level cleric spell), which I will compare to the GoF spell (cast as a 4th-level spell), states:
You call forth spirits to protect you. They flit around you to a distance of 15 feet for the duration. If you are good or neutral, their spectral form appears angelic or fey (your choice). If you are evil, they appear fiendish.
When you cast this spell, you can designate any number of creatures you can see to be unaffected by it. An affected creature’s speed is halved in the area, and when the creature enters the area for the first time on a turn or starts its turn there, it must make a Wisdom saving throw. On a failed save, the creature takes 3d8 radiant damage. On a successful save, the creature takes half as much damage.
The GoF deals 20 damage or 10 if the target succeeds the saving throw and SG deals 4d8 (3d8 + 1d8 for the extra level) and 4d8/2 if the target succeeds the saving throw. Average damage for SG is *(4*8+4)/2 = (32+4)/2 = 36/2 = 18* and 18/2 = 9 average damage if the target succeeds the throw.
Guardian of faith pros:
- Damage is higher 20>18 , 10>9
- It lasts for 8 hours, while SG lasts 10 minute
- Doesn’t require concentration, while SG does
- Great for long resting in a forest, while SG is for battling an army of goblins
Guardian of faith cons:
- Ends after 60 damage dealt, while SG doesn’t have a limit
- Doesn’t move, while SG moves with the caster and also halves enemy’s movement
- Deals damage when entered the AoE, while SG damages every turn if you stay there
That 1st con makes GoF a lot weaker. If someone chooses to ignore SG it can deal 180 damage!
If I remove the 3rd con will it make GoF overpowered? Will it be too strong, or will it be enough to be a 4th level spell?
Short Answer: No, since Guardian of Faith also deals damage to creatures starting their turn in it’s area of effect, not just the first time they enter it.
Since the third con is irrelevant, removing it would not make the spell overpowered. The key is in this line of the description:
Any creature hostile to you that moves to a space within 10 feet of the guardian for the first time on a turn must succeed on a Dexterity saving throw.
Some clarification as to why Guardian of Faith is 4th Level, and Spirit Guardians is 3rd Level:
Even though Guardian of Faith would be able to deal 60 damage to a single target, it’s total damage output remains the same, as it ends when it reaches that maximum. Also, the damage per turn does not change, the spell ends only when 60 damage is dealt, which is a major measurement of a spell’s power. Finally, consider that it still remains in place as it was cast. It cannot be moved, but it also can be specified where it will be placed, allowing for it to be placed in a strategic location. Since it isn’t tied to the spell caster’s location, and because it can last far longer than SG, this helps to place it as a 4th level spell.
For Spirit Guardians, it is at a lower spell for a few reasons. It may be able to deal more damage, but it’s duration is limited compared to GoF. With a 10 minute duration, and taking up a concentration spot, this balances out the extra damage that the spell may deal. Even though higher level spell slots can be used, the extra damage per additional level is accounted for. Another feature that makes this spell 3rd level is the area of effect. Since it is anchored to the spell caster, the spell caster has to account for the risk of being within close range to the monsters the caster would like the spell to affect.
A suggestion would be to reskin a spell with the new or changed effects under a new name. When changing around rules as written (in this case a spell), unless it isn’t enforced every time or communicated with the group as a house rule, it will cause conflict when someone expects the rule to behave one way, and the DM says otherwise.