Is this conversion of a Cloud Ray Elder CR 16?

Question

In the finale of the 3 part series on Cloud Rays, we take a look at the stat line of the largest pancake in the universe. From Pup to Adult to finally Elder, I am hoping to gain insight on the balance of these stat sheets to see if I can port them into my campaign or if they will need tweaking along the way.

Credit goes to Redditor Jambrose22/Youtuber Dungeon Dad for these conversions.

How accurate is CR 16 for this Cloud Ray Elder conversion?

Specifically, is there any concerns that pop up that might mean it is over-/under-powered for its Challenge Rating?

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Cloud Ray Elder

Gargantuan monstrosity, unaligned

Armor Class: 16 (natural armor)
Hit Points: 437 (25d20 + 175)
Speed: 20 ft., fly 60 ft. (hover)

STR - 26 (+7)
DEX - 18 (+4)
CON - 26 (+7)
INT - 4 (-3)
WIS - 27 (+8)
CHA - 8 (-1)

Damage Immunities: thunder, lightning
Condition Immunities: prone, stunned, paralyzed
Senses: Passive Perception 17
Languages: —
Challenge: 16 (15,000 XP)

Traits

Flat Body. Creatures can enter and end their turns in the same space as the cloud ray elder.

Undulating Winds. Any creature that starts its turn within 15 ft. of a cloud ray elder takes 10 (3d6) thunder damage, and it pushed 15 ft. to another space still within 15 ft. of the cloud ray elder.

Gaping Maw. Any creatures grappled by a cloud ray elder are dragged with it wherever it moves, and do not cause any form of hindrance to movement.

Actions

Multiattack. The cloud ray elder makes a sting, and thunder lash attack.

Sting. Melee Weapon Attack: +12 to hit, reach 25 ft., one target.
Hit: 18 (2d10 + 7) thunder damage and the target must make a DC 17 Constitution save, or suffer 11 (2d10) 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.

Thunder Lash. Melee Weapon Attack: +12 to hit, reach 25 ft., one target.
Hit: 29 (4d10 + 7) thunder damage and all creatures within 25 ft. of the target are pushed 15 ft. away from the primary target taking 25 (4d8 + 7) thunder damage, or half as much on a successful DC 17 Constitution save.

Scooping Bite. The cloud ray elder swoops down, its mouth agape in an attempt to grab as many creatures as possible. All creatures within a 25 ft. radius must succeed on a DC 17 Dexterity save, or take 23 (3d10 + 7) bludgeoning damage. All huge or smaller targets that fail their saving throw are grappled. The cloud ray elder can have up to three creatures grappled in its mouth at one time.

Gliding Menace (Recharge 5-6). To use this action the cloud ray elder must fly at least 60 ft. during its turn. The cloud ray elder uses the thunder lash, scooping bite, and sting actions. Each action is used during a different point in its movement. It does not provoke attacks of opportunity this turn.

Bonus Actions

Crush. As a bonus action the cloud ray elder crushes any creatures it might have grappled in it’s massive jaws.
Melee Weapon Attack: +12 to hit, all targets grappled.
Hit: 29 (4d10 + 7) bludgeoning damage.

Dream Flight (1/Long Rest). As a bonus action, the cloud ray elder teleports up to 75 ft., taking with it any creatures it has grappled. Any creatures within 10 ft. then take 19 (2d10 + 8) psychic damage, or half as much on a DC 17 Wisdom save. Any creature who fails this save is also stunned. They are allowed another saving throw at the start of each turn to recover recover.

Other questions in this series:

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

Answer 1

Estimated Overall CR: 20.

To calculate the CR, I used the reference on pages 273-279 in the DMG.

Defensive Challenge Rating: Because it has 437hp, the CR starts at 21. Because the AC is three points lower than the average for CR 21 (which is 19), we subtract 1 point from the CR for every two points of AC difference. This brings the defensive CR to 20. The Cloud Ray Elder's defense would be more effective against a party that relied on lightning or thunder damage, but generally a party is diverse enough that immunities are not considered in the CR.

Offensive Challenge Rating: The offensive CR is much more difficult to calculate because of the number of different attacks, AOE options, extended effects, and mixed attacks and saves. In 5e, saves are generally about 50% certain in balanced encounters, and common practice is to assume the AOEs hit two creatures each. With these assumptions, I calculate the average DPR of each trait as:

Undulating Winds: 20

Sting: 29 (Assuming an average of 1 turn of the additional damage)

Thunderlash: 66 (Assuming half of the creatures successfully save, on average)

Scooping Bite: 23 (Assuming half of the creatures successfully save, on average)

Crush: 58

Dream Flight: 38

Choosing the best option for each action/bonus action yields a DPR of 173 with a +12 to hit. This equates to an offensive CR of 22. However, this combination is unlikely to occur in actual combat. Instead, if we assume the Cloud Ray Elder only uses its Multiattack, the DPR is 95. This equates to an initial CR of 15. The attack bonus is 6 points higher than the average for a CR 15, so the offensive CR is adjusted to 18. Most situations will be somewhere between these two extremes, so I will average these two values to get an offensive CR of 20.

Overall CR: Averaging the offensive and defensive challenge ratings of the Cloud Ray Elder yields an overall CR of 20*.

To reduce the CR, I would recommend decreasing Cloud Ray Elder's hp and decreasing the number or damage of its attacks and traits.

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*Using the more conservative estimations for the Cloud Ray Elder's offensive abilities, the CR averages to 19. In the best case scenario for the Cloud Ray Elder (using the offensive CR of 22), the overall CR is 21.