Does the Black Tentacles spell do damage twice at the start of turn to an already restrained creature?

Question

The spell Black Tentacles (listed as Evard's Black Tentacles on PHB p. 238) has the following text:

When a creature enters the affected area for the first time on a turn or starts its turn there, the creature must succeed on a Dexterity saving throw or take 3d6 bludgeoning damage and be restrained by the tentacles until the spell ends. A creature that starts its turn in the area and is already restrained by the tentacles takes 3d6 bludgeoning damage.

Each of the two sentence has a condition that results in damage. Note that there is no "or" or "instead" in the second sentence. The second condition is more specific than the first, but it never says they're exclusive.

Does this mean a creature starting its turn restrained by the tentacles receive the damage twice?

Answer 1

My reading of the spell is that it is poorly worded, and that the two scenarios:

a creature enters the affected area for the first time on a turn or starts its turn there, the creature must succeed on a Dexterity saving throw or

and

A creature that starts its turn in the area and is already restrained by the tentacles

are intended to be two alternatives for reaching the damage condition, even though they overlap on a reasonable strict reading of the text.

The power disparity with other area-affecting damage spells of the same level is due to the restrained condition leading to auto-damage, whilst other similar area control plus damage spells do not prevent moving away, just encourage it. There is no need (and it seems too powerful) to re-apply the first saving throw plus damage to a creature that is triggering the second condition.

I would actually change the first sentence to:

[Suggested] When a creature that is not already restrained by this spell enters the affected area for the first time on a turn or starts its turn there, it must succeed on a Dexterity saving throw or

Now clearly that is not RAW, and I have no indication from other sources that this is a correct interpretation. However, I think the argument from game balance is a strong one. Note this can still lead to a creature becoming restrained and taking the damage twice in a round, if for instance it is pushed into the area of the spell on another creature's turn.

This is how we play spell in my group, and it is still a preferred spell for 7th level Wizards.

Answer 2

Yes, it can receive up to 6d6 dmg

My first interpretation would be that the last sentence refer to the damage you take when you fail your DEX save, which you automatically take because you are already restrained. Either way, you take 3d6 damage or nothing on your turn.

This is what I've used all this time and I didn't consider the second interpretation: the last sentence is in addition to the other sentence, dealing total 6d6 damage. Succeeding the DEX save on the start of your turn reduce the damage to 3d6 damage that turn.

I checked the other 4th level wizard spells to compare the power level:

• Wall of fire deals 5d8 dmg per turn, multiple target, no condition
• Storm sphere deals 4d6 dmg per turn, single target, disadvantage to perception check
• Black tentacles deals 3d6-6d6 dmg per turn, multiple target, restrained

I find that the second interpretation makes black tentacles too powerful, however based on the wording, it seems to be the right interpretation. As for me, I will keep using the first interpretation to keep the spell's power level balanced.