You attempt to reshape another creature’s memories. One creature that you can see within range makes a Wisdom saving throw. If you are fighting the creature, it has Advantage on the save. On a failed save, the target has the Charmed condition for the duration. While Charmed in this way, the target also has the Incapacitated condition and is unaware of its surroundings, though it can hear you. If it takes any damage or is targeted by another spell, this spell ends, and no memories are modified.
While this charm lasts, you can affect the target’s memory of an event that it experienced within the last 24 hours and that lasted no more than 10 minutes. You can permanently eliminate all memory of the event, allow the target to recall the event with perfect clarity, change its memory of the event’s details, or create a memory of some other event.
You must speak to the target to describe how its memories are affected, and it must be able to understand your language for the modified memories to take root. Its mind fills in any gaps in the details of your description. If the spell ends before you finish describing the modified memories, the creature’s memory isn’t altered. Otherwise, the modified memories take hold when the spell ends.
A modified memory doesn’t necessarily affect how a creature behaves, particularly if the memory contradicts the creature’s natural inclinations, alignment, or beliefs. An illogical modified memory, such as a false memory of how much the creature enjoyed swimming in acid, is dismissed as a bad dream. The DM might deem a modified memory too nonsensical to affect a creature.
A Remove Curse or Greater Restoration spell cast on the target restores the creature’s true memory.
Using a Higher-Level Spell Slot. You can alter the target’s memories of an event that took place up to 7 days ago (level 6 spell slot), 30 days ago (level 7 spell slot), 365 days ago (level 8 spell slot), or any time in the creature’s past (level 9 spell slot).
This spell is full of Tom foolery and I wish to abuse it.
I compiled a list of possible ways to use this spell. Please help me improve this list.
Change recent memory of an important figure telling the target that an adventuring party is expected to arrive, and he/she should allow access, escort in, or aid in any manner.
Change the memory of a guard that the Captain of the Guard ordered the release of prisoners.
Change the memory so that the party provided a certain required item (important document, gold, shown a badge).
Change the memory of a failed social interaction.
Cover up a failed theft attempt by changing the memory of how the target lost the item, then just take the item.
Bolster relations by creating last night’s dream about how the adventuring party arrived to save the day or aid with a quest.
Create a cover up to circumvent an expected detect thoughts encounter.
Remove the memory of an interrogation before releasing prisoner, and possibly replace the memory with an escape.
Create a traumatizing memory from the target’s past (to be evil or vindictive).
Remove a traumatizing memory from the target’s past (probably higher level).
Remove a witness without killing them.
Create a false witness.
Cast modify memory on a prepare caster and make them forget what spells they prepared.
Going at the top of my list....
A lot of potential use for this spell, especially when upcasted.
The main thing keeping it in control (assuming the caster keeps it reasonable in the first place) is just that "that lasted no more than 10 minutes" time limit of what you can alter, which doesn't increase even when upcasted.