Swift Kick in the Rear from Beyond

Verbal Component: A dark, ominous and reverberating incantation derived from Infernal that roughly translates into "DON'T MOVE!"

1st effect: All creatures with at least 7 INT within 30 ft, friend or foe, including target (but not caster), that can hear the word spoken by the caster (i.e. not already Deafened) must immediately make a WIS save. No effect on success or against any creature with 6 or less INT, on a failed save creature takes 2d10 Psychic damage and is Deafened and Frightened until the end of your next turn, and creature's backside will feel numb (no additional detrimental effects) until they finish a long rest. All repeating effects do not stack.

2nd effect: The intended target of this spell must make both an INT AND a WIS save (separate from the 1st effect). On a failed INT, target takes 5d8 Psychic damage with the sensation of their entire body being crushed, and is Paralyzed, Deafened, and Frightened until the end of your next turn (though they can attempt a WIS save on their turn to remove the Paralyzed condition, except if they realize what they were just hit with, they probably will prefer to stay Paralyzed). On a successful INT, target takes half damage and is only Frightened. On a failed WIS, target takes 5d8 Necrotic damage with the sensation of having a hole drilled imprecisely through their head (or equivalent appendage), and is Blinded, Deafened, and Frightened until the end of your next turn. On a successful WIS, target takes half damage and is only Deafened. This effect applies to the target even if they have been Deafened by the 1st effect or were previously Deafened, and regardless of INT.

3rd Effect: If the target successfully saved both INT and WIS, target immediately takes 2d10 bludgeoning damage and 2d10 fire damage upon their backside from an unseen (and unseeable) demonic force, not mitigated by armor but can still be halved by resistances, and no further effect takes hold. If the target failed EITHER of these saves, the true effect of this spell takes hold of them and remains in effect until dispelled or triggered, with no time limit.... They are locked into the sights of an extra-dimensional Speed Demon that has been racing at insanity-inducing speeds along the outer edges of the Hells since time immemorial, and wants to see the target make any movement at all, because that will be its permission to blink into their plane of existence and strike (written into its eternal damnation contract, its devilish lawyer was able to give it something to look forward to). When this target takes any action (even casting a spell or cantrip without any verbal or somatic components), any reaction, any bonus action, any move action which includes twitching a finger or turning their head, anything that is not the most subtle of movements such as very carefully talking (or very carefully screaming), and also if they are moved by an external source in any way, within the space of half a blink, the demon appears, moving at full speed, somehow bypassing even the most meticulous of anti-magic or extra-dimensional defenses, and with immaculate precision, kicks the target directly upon (and likely through) their posterior with a flaming, adamantine, eldritch-enriched cloven hoof (it kicks righty, if you must know), which deals 4d20 bludgeoning damage and 3d20 fire damage, not able to be resisted or mitigated in any way, and unless of Huge or greater size (if so they instead fall forward Prone instantly, likely falling upon and crushing a few extra targets), will also thrust the target forward and vaguely upward 2d10000 (2d100x100) ft at their terminal velocity, which is likely to cause further damage to the target as if it were taking falling damage from maximum height if there are any structures or obstacles in the way, unless they are able to travel the full distance unobstructed and afterwards are still alive and somehow are able to stop themselves from further splattery results. The demon in the next available instant after the full follow-through will return to its eternally tormenting origin in glorious triumph to resume its endless circuit, though anecdotes exist that it hoots and hollers very loudly along its path and holds its arms high in a victory pose for weeks afterwards. It has been observed, gleefully, that if the first effects prove to outright kill the target, its lifeless husk flopping over is still enough to trigger the demon's field-goal attempt, and usually results in complete concussive liquification of all that once was your hapless victim.

Note: This spell effect is triggered only upon any movement after the 3rd effect has taken hold on the target, which happens instantly upon either saving throw showing a failure, thus if target remains Paralyzed and does not more or get moved after that effect ends, there is a window for dispelling the effect which will allow the target to move and act normally again without suffering humiliating annihilation, though such will have to be done by an external power, as the target taking any action, we've been over this, will result in above hilarity.

Additional Note: After a target has been declared and the spell cast, regardless of ultimate fate of target, this spell cannot be cast on this target again by the same or any other caster for one (1) entire solar year (Faerun reckoning) from the date of being targeted, it will instantly fail and no effect will take hold on target. The 1st effect will still happen to adjacent creatures, but the original target, through some quirk of the magic, will be completely immune to even that. Additionally, this spell can only be successfully cast by any mage on any plane of existence once every 7 days regardless of target, possibly due to the demon being required to run a certain distance between interdimensional interruptions, and though a caster might attempt to prepare or otherwise make ready this spell again as early as the next day as per usual, part of that prep work will reveal if the casting will potentially be successful, or if the demon is on a break and only the 1st effect will take place, the 2nd part will fail and be wasted, thus lowering its potential power and usability.

Final Note (as no additional writings have been found and spell author can no longer be located on any known plane of existence): And before you think you're so clever, the kick cannot be prevented or blocked or deflected in any way, even should an immovable object be in the way, its been seen to phase through any potential obstacles on its inexorable mission to make sure that its hoof will always find the intended rump at full force! Nor can the demon or its powerful hooves be harmed or damaged in any manner, nor will any potential means of trapping or slowing down this demon bear any fruit besides making you a laughingstock among your peers for wasting your time and resources on a completely pointless endeavor, its practically a pillar of creation at this point, the demon's contract which is bound by the blood of multiple lords of the Hells will not allow it, probably not until they are annihilated and most of existence is unmade, so stop trying to steal its only source of fun and let the casters use it for the greatest humiliating punishment that a mortal can inflict upon the most deserving foppish toads like you! Who's laughing now, Octavius?! ME! Cuz you're busy being a greasy SMEAR on the ceiling! And I hope someone comes along to scrape you off and resurrect you, so you can quiver in fear for the rest of your pathetic, worthless existence, or at least until next year and I can find you again to bring my favorite fiend to the explody punting party! We can make it an annual tradition! I'll teach my kids this spell, and they will cheer as you pop overhead like a firework! That'll teach you to accuse me of cheating on my exams! That'll teach you ALL THE WAY TO--