Is CR 8 accurate for this conversion of a Cloud Ray Pup?

Question

So I have been running a campaign that I wanted to focus in on a super cool unique "monster" that the party could utilize for narrative, combat, and transportation purposes. So I looked through my old D&D books and found the Cloud Ray (D&D 3.5 Monster Manual II, Pg 49). This Dark Sun campaign creation is (in my opinion) the Sky Whale of D&D. And I wanted to see how you'd go about converting a 3.5/4e monster to 5th edition.

Luckily, I didn't have to. Another enterprising DM (Reddit: jambrose22 or YouTube: Dungeon Dad) converted them for me.

How accurate is CR 8 for this Cloud Ray Pup conversion?

Are there any tricks or traps that make it over-/under-powered for its given Challenge Rating of 8?

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Cloud Ray Pup

Large monstrosity, unaligned

Armor Class: 17 (natural armour)
Hit Points: 152 (16d10 + 64)
Speed: 15 ft., fly 50 ft. (hover)

STR - 20 (+5)
DEX - 24 (+7)
CON - 18 (+4)
INT - 2 (-4)
WIS - 20 (+5)
CHA - 10 (+0)

Damage Resistances: thunder, lightning
Condition Immunities: prone, stunned, paralyzed
Senses: Passive Perception 15
Languages: —
Challenge: 8 (3,900 XP)

Traits

Dream Resurgence (1/long rest). When a cloud ray pup is reduced to 0 hit points, it vanishes into a cloud of ether. At the start of its next turn, it reappears somewhere within 50 ft. of its last location with 1 hit point. Any abnormal conditions such a being poisoned or exhaustion or removed from the pup.

Actions

Gliding Attack. To use this action the cloud ray pup must fly at least 50 ft. during its turn. The cloud ray pup uses the sting action any point during its movement and does not provoke attacks of opportunity this turn.

Sting. Melee Weapon Attack: +10 to hit, reach 15 ft., one target. Hit: 15 (2d8 + 7) thunder damage and the target must make a DC 14 Constitution save, or suffer 9 (2d8) lightning damage at the start of each of its turns. The target may attempt this saving throw again at the end of each turn. If the target fails their saving throw by 5 or more, they are also paralyzed.

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Related:

• How balanced is this conversion of a Cloud Ray Adult?
• How balanced is this conversion of a Cloud Ray Elder?

Answer 1

The initial check uses the rules for creating monsters in the DMG, pages 273-279, to determine what the CR would be.

Defensive Challenge Rating: Based on the average hit points, we initially start with a CR of 6. Since the AC for your cloud ray is two higher than the average for a CR 6, that adjusts the Defensive CR up by 1, to 7. This is open to interpretation, since there are resistances and immunities involved. Generally speaking, you shouldn't worry about immunities unless they crop up often enough to impact a significant number of attacks, meaning that they can be ignored (for CR purposes) as long as your campaign doesn't involve a whole lot of lightning. If it's based entirely around the Plane of Air, that would be something else.

Offensive Challenge Rating: The average damage per round would be 16 (9 for the 2d8, + 7 for the Dex bonus) thunder and 9 lightning, or about 25 per round. That's a CR 3, offensively. Normal CR 3 critters have an attack bonus of +4, so your cloud ray's +10 adjusts this upward to a final offensive CR of 6.

Cloud rays also have a set of abilities that could impact their CR- their dream resurgance, gliding attack, and the paralysis caused by their sting. To check that, we should do our best to match these abilities to the typical monster features on pages 280 and 281. These are also open to interpretation, but I decided they were closest to Rejuvenation, Flyby, and couldn't find a good match for the paralysis, so I've left it off. Neither Rejuvenation or Flyby affect the calculation of CR meaningfully, leaving the average calculated CR at 6.5, so it could be considered a strong CR 6 or a weak CR 7... not an 8.

To further check, let's compare the cloud ray to other creatures of similar CR. We're preferably looking for one that matches the cloud ray roughly- a flying monstrosity with a single attack and one variety of elemental resistance.

The closest I could get was the dragon. Both Bronze and Green Young Dragons are CR 8 and can fly, have an affiliation with elements, and are Large creatures. A Young Green Dragon, calculated the same way I did above, would clock in at (Defensive CR 6, Offensive CR 6, abilities shift them to 8 and about 9 respectively) about 8.5. The bronze dragon is slightly higher. Both sit fairly closely to their given CR (8). Both could, at a quick "top of my head" comparison, make short work of a Cloud Ray Pup.

In short, for a CR 8 creature, your Cloud Ray Pup is under-powered.

On the topic of adjustments to make to this creature- if you'd like to follow the original cloud ray's strengths, cloud rays had obscene Strength scores, better Constitutions than dragons of similar CR, and about double the hit points of a similar dragon... but their Dexterity was strictly average and their AC was low enough that even at full size, the CR 16 Cloud Ray from 3.5 could reliably be hit by a level 1 wizard with a staff. They didn't have lightning immunity, nor did they deal lightning damage or paralyze. My suggestion would be to move this cloud ray closer to its roots- lower the Dexterity, increase the Strength, give the hit points a massive boost so that the majority of its CR 8 score comes from them. Instead of the Sting that this cloud ray has, give it a slam attack that's powered by its Strength, and a bite attack it can use the same round. The original cloud ray had a low-level telekinetic ability; this one could have mage hand without changing the CR at all. Last, I'd actually make it a bit bigger; the original cloud ray at full size was big enough that it could swallow two Huge creatures, and even shrinking it down to "pup" size, I'd imagine it would still easily be Huge itself.