Does a Staff of the Magi Fireball penetrate Globe of Invulnerability?

Question

Globe of Invulnerability reads, in part (emphasis mine):

Any spell of 5th level or lower cast from outside the barrier can't affect creatures or objects within it, even if the spell is cast using a higher level spell slot.

Okay, so a level 6+ spell penetrates the barrier. Normally, "a level 6+ spell" would include ANY spell cast using a level 6+ slot. Globe of Invulnerability has that extra "even if..." clause, though, so that we still check Fireball's base level even when it's cast with a level 6 slot. Great. This was all covered in this related question.

The question I'm writing now, though, comes down to whether that "even if..." clause can be circumvented by upcasting the spell with something other than a slot. Enter The Staff of the Magi:

While holding the staff, you can use an action to expend some of its charges to cast one of the following spells from it, using your spell save DC and spellcasting ability: conjure elemental (7 charges), dispel magic (3 charges), fireball (7th-level version, 7 charges)

Interpretation 1: That fireball IS a level 7 fireball. That's what the staff's description says. That fireball is NOT a "spell of 5th level or lower". Moreover, that level 7 fireball was NOT cast using a higher level slot, so it doesn't run afoul of the Globe's "even if..." clause. The fireball penetrates

Interpretation 2: The fireball is normally a level 7 spell, but that's per the rule about casting spells with higher level slot. Let's look at the actual rule:

When a spellcaster casts a spell using a slot that is of a higher level than the spell, the spell assumes the higher level for that casting. For instance, if Umara casts magic missile using one of her 2nd-level slots, that magic missile is 2nd level (PHB p.201).

One might argue that the Globe's "even if..." clause means that it's an exception to the above rule. The fireball fails to penetrate.

Interpretation 3: When The Staff of the Magi says, "7th-level version", it means that, with respect to all other rules or exceptions-to-rules or whatever, pretend like the spell was cast from a level 7 spell slot (just don't cross of a level 7 slot if you have one). The fireball fails to penetrate.

Staff of Power On a lighter note, what got me thinking about this was encountering a Staff of Power in-game, which can (among other things) cast Globe of Invulnerablity. It's only a Very Rare staff, whereas the Staff of the Magi is legendary. I find it interesting to see the little advantages the Staff of Power has over the Staff of the Magi.

Answer 1

No, because functionally, the staff is using a higher-level spell slot.

The notation "fireball (7th-level version)" should be read as shorthand for "fireball (as if cast with a 7th-level spell slot)". To see why, look at fireball itself:

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.

Note that this doesn't say "When this spell is cast at 4th level or higher", even though it is 4th level or higher when a higher-level spell slot is used (PHB p. 201, as you noted). The extra damage specifically depends on the level of the spell slot used.

As far as I can determine, all upcastable spells describe their enhanced effects as depending on the spell slot level, not the spell level. Just spot-checking the first five upcastable spells I see in no particular order, healing word, longstrider, invisibility, counterspell, and dispel magic are all worded this way. (If anyone knows of an exception, please say so.)

So what's the Staff of the Magi doing, since it doesn't use spell slots? Well, one option is that a "fireball (7th-level version)" is the same thing as a regular fireball, but I don't think anyone interprets it that way. The intended reading is almost surely that it's a fireball that does 12d6 damage, which must be cast with a 7th-level spell slot, so that's what the Staff produces: a fireball cast with a 7th-level spell slot.

As such, globe of invulnerability treats it as a 3rd-level spell and blocks it.

Answer 2

No

Spells from items are cast using spell levels (DMG p.141) with the implication that they can be cast at a higher level:

The spell is cast at the lowest possible spell level, ... Certain items make exceptions to these rules ...

The Staff of the Magi is an item that does make an exception: "fireball (7th-level version, 7 charges)". So, the Staff casts the 3rd level spell Fireball at higher than the "lowest possible level" making it a 7th level spell.

Then the Globe of Invulnerability steps in with its exception: "Any spell of 5th level or lower cast from outside the barrier can't affect creatures or objects within it, even if the spell is cast using a higher level spell slot." This is a 3rd level spell using a 7th level slot - it cannot penetrate the Globe.

Answer 3

Yes, because the Staff doesn't have Spell Slots.

PHB pg. 201 Spellcasting:

When a spellcaster casts a spell using a slot that is of a higher level than the spell, the spell assumes the higher level for that casting. For instance, if Umara casts magic missile using one of her 2nd-level slots, that magic missile is 2nd level.

However, since the specific restriction is, even if the spell is cast using a higher level spell slot, the Staff doesn't care because it doesn't use spell slots. It uses charges.

So the character casts a 7th level Fireball, the Fireball hits the Globe and it bypasses the Invulnerability because the check applies only to spells upcast using spell slots.

Answer 4

Staff of Magi's Fireball is a 7th level spell that is not cast with spell slots

The language around spells can be difficult to understand. There are several similar and related concepts that are confusingly named.

Spell levels, spell slot levels, and spell levels (again)

Let's get this terminology straight.

Firstly there is the 'spell level', as stated on the spell's entry. Secondly there is the 'spell slot level', which you use to cast the spell. Lastly, there is the 'spell level' again, this time referring to the version of the spell being cast.

Upcasting results in a spell of a higher level

The rules for casting with a higher spell slot state:

if Umara casts magic missile using one of her 2nd-level slots, that magic missile is 2nd level.

In this example magic missile is a 1st level spell. It has been cast with a 2nd level spell slot. The resulting spell is the 2nd level version of magic missile.

Spells cast with items don't (and can't) use spell slots

Characters have spell slots, and when a spell is cast under normal circumstances, the spell slot is expended. Items do not have spell slots, there are no rules that say they do, there is nothing that implies they do. They use a separate mechanic called "charges".

The 7th level version of fireball is a 7th level spell, and was not cast with spell slots at all.