Can you activate a spiritual weapon while inside the effect of Otiluke's Resilient Sphere?

Question

One of the rules for the Resilient Sphere spell states:

Nothing—not physical objects, energy, or other spell effects—can pass through the barrier, in or out, though a creature in the sphere can breathe there. The sphere is immune to all damage, and a creature or object inside can’t be damaged by attacks or effects originating from outside, nor can a creature inside the sphere damage anything outside it.

What if the person trapped inside of the sphere had cast a spell like Spiritual Weapon?

I believe the sphere would prevent you from casting Spiritual Weapon once you are inside of it. But what about activating it if you have cast it before entering the sphere?

Answer 1

Whether you can move the spiritual weapon depends on whether moving it involves targeting the destination

A resilient sphere (much like a wall of force) provides total cover, and thus the rules on "Total Cover" apply:

A target with total cover can't be targeted directly by an attack or a spell, although some spells can reach such a target by including it in an area of effect. A target has total cover if it is completely concealed by an obstacle.

This means that somebody inside the sphere can not target anything outside the sphere with an attack or spell. However, it is unclear whether moving a spiritual weapon counts as targeting a location; a question that is more discussed here, and leaves it unclear whether you can actually move the spiritual weapon:

• Can spells with movable areas of effect be moved out of sight or behind obstacles?

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Whether you can attack with the spiritual weapon depends on where the attack "originates from"

The rules on "Cover" and "Total Cover" state:

A target can benefit from cover only when an attack or other effect originates on the opposite side of the cover.

A target with total cover can't be targeted directly by an attack or a spell

This ends up coming down to whether or not you believe the attack originates from the spiritual weapon or the caster. If it originated from the weapon then no sort of cover can apply so the attack will go off just fine. However, if the attack originates from the caster then the target of the attack (thus a target of the spell) has full cover and cannot be targeted (thus cannot be attacked).

I would rule that it cannot be made to attack

The description of spiritual weapon describes the summoned weapon as being used by the caster, which leads me to believe that the attack originates from the caster (whatever that means):

[...] When you cast the spell, you can make a melee spell attack against a creature within 5 feet of the weapon. On a hit, the target takes force damage equal to 1d8 + your spellcasting ability modifier [...]

[...] As a bonus action on your turn, you can move the weapon up to 20 feet and repeat the attack against a creature within 5 feet of it [...]

Answer 2

First of all, as pointed out in the question about moving areas of effect linked in Medix2's answer, there is some ambiguity as to whether spells like Spiritual Weapon can be controlled at all through any kind of total cover. Obviously, if the DM rules that they cannot, then Resilient Sphere completely prevents a creature inside the sphere from controlling their Spiritual Weapon outside it. So, that being said, for the remainder of this answer, let's assume your DM has ruled that existing movable spell effects are not limited by line of effect unless otherwise noted, so that, for example, you would be allowed to send your Spiritual Weapon over a 10-foot-high wall to attack someone on the other side even though the wall blocks direct line of effect from you to the target. With this in mind...

I would rule that an existing Spiritual Weapon continues functioning normally

Assuming, as described above, that line of effect is not an issue, nothing about the barrier of a Resilient Sphere spell prevents you from controlling an existing Spiritual Weapon through the barrier. The main problem is the final clause of the spell's 2nd paragraph (highlighted in bold):

Nothing–not physical objects, energy, or other spell effects–can pass through the barrier, in or out, though a creature in the sphere can breathe there. The sphere is immune to all damage, and a creature or object inside can't be damaged by attacks or effects originating from outside, nor can a creature inside the sphere damage anything outside it.

Taken alone, this clause clearly seems like it would prevent you from doing any damage with your Spiritual Weapon while trapped in the sphere. (Taking it ultra-literally, you could still attack and hit with it, but all the damage would be prevented.) However, consider that the entire paragraph is dedicated to describing the nature of the barrier and what can and cannot pass through it. Taken in context, I don't see any reason to read this final clause any more broadly than this: just like the rest of the paragraph, this clause only applies to effects that (try to) pass through the barrier. Reading the final clause of a 3-clause sentence as applying more generally than either of the other 2 clauses in the sentence or the remainder of the paragraph would not be a reasonable reading of a plain English sentence.

Hence, unless your DM rules that line of effect from the caster is required for re-targeting of ongoing spell effects, nothing in the Resilient Sphere spell prevents you from using your bonus action to attack and deal damage as normal with your Spiritual Weapon even while trapped inside the sphere. Similarly, a druid that had already cast Call Lightning before being trapped could continue using their action to call down lightning bolts on creatures outside the sphere, a cleric who had already cast Dawn could continue moving it as a bonus action and dealing damage with it, and so on.

Answer 3

Controlling the weapon falls under "Other Spell Effects"

Let's suppose a spiritual weapon already exists, and then the character who cast it ends up in the sphere.

Issuing an order to attack requires spending an action. This represents the caster manipulating the magic in order to get it to do something. Thus, attempting to do so fails because the command to attack cannot leave the sphere.

The action is an attack made by the person in the sphere

The description says you can spend an action to (among other things) make an attack. But "a creature inside the sphere [cannot] damage anything outside it". In other words, the spell isn't independently taking actions. It is an extension of yourself. Therefore the weapon's attacks cannot damage anything outside the sphere.

Answer 4

By RAW, I would say no because:

[...] you make a melee spell attack [...]

So it's still magic, some form of energy, that activates the weapon and the sphere blocks all spell effects and energy.

Also to do a melee attack you usually need to see the target. The Spiritual Weapon is not automatically attacking a target on its own will. Attacking in a Darkness area give you disadvantage and you do not know whether you miss or no one was there... If you do get a hit, you deal damage so you know you hit something. It could be someone in your party, though.