Is this Waking Dream spell balanced?

Question

This homebrew spell for dnd 5e is based largely on the Scrying spell and the Dream spell. Conceptually, I wanted something that functions similarly to the "force-bond" that Rey and Kylo Ren share in the Star Wars sequel trilogy.

Is this spell balanced? Are there any class lists that shouldn't have access to this spell? Are there any notable exploits?

Note that the spell only functions while both parties are conscious, making long-distance assassinations difficult. Similarly, the wording prevents one from casting a high-level Witchbolt and continuing to apply damage after the Waking Dream ends. It would allow a dangerous spellcaster (like Strahd) to solo one party member down to unconsciousness, but that shouldn't be deadly, especially if surrounded by friends.

Waking dream
5th level Illusion

Casting Time: 1 minute
Range: Special
Components: V, S, M (a focus worth at least 1,000 gp, such as a crystal ball, a silver mirror, or a font filled with holy water)
Duration: Concentration, up to 10 minutes

You step into a creatures vicinity, visible and tangible only to them. Choose a creature known to you as the target of this spell. The target must be on the same plane of existence as you, and you must both be conscious when the spell is cast. If the caster or the target becomes unconscious, the spell immediately ends. The target must make a Wisdom saving throw, which is modified by how well you know the target and the sort of physical connection you have to it. If a target knows you're casting this spell, it can fail the saving throw voluntarily if it wants to be contacted.

\begin{array}{|c|c|}\hline \textbf{Knowledge} & \textbf{Save Modifier}\\\hline \text{Secondhand (you have heard of the target)} & \text{+5}\\\hline \text{Firsthand (you have met the target)} & \text{+0}\\\hline \text{Familiar (you know the target well)} & \text{-5}\\\hline \end{array}

\begin{array}{|c|c|}\hline \textbf{Connection} & \textbf{Save Modifier}\\\hline \text{Likeness or picture} & \text{-2}\\\hline \text{Possession or garment} & \text{-4}\\\hline \text{Body part, lock of hair, bit of nail, or the like} & \text{-10}\\\hline \end{array}

On a successful save, the target isn't affected, and you can't use this spell against it again for 24 hours.

On a failed save, an illusion of you appears in view within 10 feet of the target, while an illusion of the target appears in an equivalent position relative to you. Both illusions mirror the actions and words of their image. Only you and the target can see, hear, and interact with these illusions, and both you and the target have no perception of the other person’s true surroundings.

For you and the target, it is as if the other were actually there, including for the purposes of attacking, targeting spells, and other effects, though other concentration spells cast end if the target is no longer in casting range when this spell ends. Any damage taken by the illusion is taken by its mirror creature. Objects can also be transferred from one location to another with this spell if they are on the illusion’s person when this spell ends.

Finally, should any edits be made to wording to make this spell more clear?

Answer 1

I believe there are a few major balance issues with this spell in its current form. I don't believe I have the experience necessary to suggest appropriate changes to balance the spell, so I will limit myself to just pointing out the obvious and likely unintentional exploits.

Despite your best attempts, this is still a "Scry n' Fry" spell

You've added a number of limitations to prevent the use of this spell as a tool for long-distance assassination, but unfortunately there are still loopholes. One obvious one is that an instant-kill spell like Power Word Kill or Disintegrate completely bypasses the limitation that the spell ends when a creature is knocked unconscious. If you don't need the target dead, but rather just out of the way, spells like Contagion and Feeblemind will also serve equally well.

Leaving aside deadly spell combos, any attack or other effect that inflicts ongoing damage (e.g. an attack that sets the target on fire) will kill the target in short order if they are knocked unconscious. Finally, simply bringing the target to zero hit points has a decent chance of killing them from failing 3 death saving throws.

In short, there are lots of ways to assassinate someone using this spell, without even getting especially creative. As a bonus, no one can trace the murder back to you, since only the target saw you.

Unrestricted long-distance transfer of objects is not normally available at 5th level

The ability of the spell to transfer objects over long distances is also potentially unbalanced. The lowest-level spell that even comes close to replicating this feature is Teleport, a 7th-level spell. Notably, Teleport allows the transport of up to 9 creatures, but specifically limits object transport to a single object per casting. At 5th level, we have Teleportation Circle, which can (with some creativity) be used to teleport objects, but only if the destination is a permanent teleportation circle, a major limitation. And druids have the 6th-level spell Transport Via Plants, which could be used similarly to Teleportation Circle with somewhat less stringent limitations.

The point of this is that precisely-targeted long-distance teleportation of objects is an ability that simply isn't available in existing 5th level spells. Furthermore, this spell allows the teleportation of not just single objects, but as many objects as a creature can hold. This spell is a (waking) dream for a wizard & rogue duo planning a heist.

Does this actually need to be a spell?

Depending on what your plans are for this spell, you might not need it to be a spell at all. Do you actually want it usable by players? If not, it might be better to give it to the BBEG as a once-per-long-rest "magic ability". If only you as the DM can use it, you don't have to work as hard to balance it, because you can balance it on the fly in the same way you do everything else. For example, you don't have to think as hard about the object transfer mechanics, because you control which objects the BBEG will decide to transfer and can make sure not to transfer anything that breaks the plot or short-circuits a quest.

Of course, if you intend for this to be learnable and usable by PCs, then you can't get around balancing it properly as an appropriate-level spell.