Can a Wild Magic Barbarian restore a 7th(+) Level Warlock's spell slots?

Question

In the recently released preview of the Wild Magic Barbarian that will be in Tasha's Cauldron of Everything (preview here), I noticed the 6th level feature 'Bolstering Magic'. This feature has two applications. One acts as a Bless-type option, the second one reads:

Roll a d3. The creature [you're touching] regains one expended spell slot, the level of which equals the number rolled or lower (the creature’s choice). Once a creature receives this benefit, that creature can’t receive it again until after a long rest.

Suppose this effect is used on a Warlock of level 7 or above, and for the sake of argument suppose we rolled a 3 on the d3. All of their spell slots are of spell level 4. What happens?

• Nothing, the Warlock doesn't have the right type of spell slot to regain
• The Warlock has (expended) spell slots of Level 4 and higher, and now has a level 3 spell slot
• Something else happens, namely ...

Answer 1

While not a RAW answer, I would consider how the pearl of power works and has been errata'd over time in this scenario.

The original text of the item read:

You can use an action to speak this pearl's command word and regain one expended spell slot of up to 3rd level.

Over time, Crawford suggested that warlocks should be allowed to regain slots with a pearl of power, though with the phrasing being a personal ruling moreso than an official one:

I'd allow a pearl of power to take an expended spell slot of 4th level or higher and turn it into a 3rd-level slot.

This was eventually errata'd into the item itself, whose text now begins with:

While this pearl is on your person, you can use an action to speak its command word and regain one expended spell slot. If the expended slot was of 4th level or higher, the new slot is 3rd level.

While it's certainly possible that the lack of such text in the new barbarian ability may have been intentional, historically it seems they haven't had a problem with restoring warlock spell slots at a lower level when such a feature is available.

Additionally, I would consider the transition from party level 6 to 7 in the scenario where warlocks are the primary/only spellcaster in a party with a Wild Magic barbarian; that part of the feature would effectively suddenly "turn off" at level 7 if restoring lower-level slots is not permitted, which is quite awkward.

Answer 2

RAW nothing would happen.

The feature only does what it says it does. From the section you quoted (emphasis mine):

The creature [you're touching] regains one expended spell slot, the level of which equals the number rolled or lower (the creature’s choice).

Since the Warlock cannot regain a spell slot of level 3 or lower, nothing happens.

Answer 3

The first dot point is correct. The feature says the creature “regains one expended spell slot, the level of which equals the number rolled or lower”; the Warlock in question has no expended spell slots that meet the level requirement, so they cannot regain them. The feature doesn’t say it grants new spell slots, so the warlock gets none at all.

This is functionally the same as a wizard who has only used a third level spell slot who is the target of the feature when a 1 or 2 is rolled. They have no applicable expended spell slots, and so they regain none.

Despite the comma, I think it’s clear the level of the spell slot is a restriction on what spell slot can be recovered, not assigning a level to it after the fact. The wording of the wizard’s Arcane Recovery feature is similar:

Once per day when you finish a short rest, you can choose expended spell slots to recover. The spell slots can have a combined level that is equal to or less than half your wizard level (rounded up), and none of the slots can be 6th level or higher.

The levels of the spell slots here are described in a separate sentence, but again I think it is clear this is a restriction on which spell slots can be recovered, not an alteration of them.