Bowgentle's Book from “Pages From the Mages” makes a cameo in Lost Mine of Phandelver in the D&D 5th Edition Starter Set. If the characters ever find this book, it will contain a couple of unique spells, including Bowgentle's Fleeting Journey. I've created a 5e spell inspired by the one from “PFtM”:
Bowgentle's Fleeting Journey
Casting Time: 1 action
Components: V, S, M (a small ball of uncured rubber)
Duration: 1 round
You touch one creature other than yourself and choose a location that you can clearly see within 500 feet. The creature is instantly teleported to that location along with anything it is wearing or carrying. If the creature is unwilling, you must make a melee spell attack. At the start of your next turn, the creature is teleported back to its original location. The creature can otherwise perform actions normally for the duration.
A maximum of 500 pounds of creature and equipment can be transported by this spell. If the creature is Grappled, Restrained, or loaded with more weight than it can carry, the teleportation fails.
If the return location is occupied by another creature or object when the duration ends, the target of this spell does not return to that location and must make a Charisma saving throw or be pushed into the Astral Plane. On a successful save, the target takes 4d6 points of force damage.
At Higher Levels. If this spell is cast with a slot of 6th level or higher, for each level above 5th the maximum teleport distance increases by 250 feet, the maximum weight by 250 pounds, and the duration increases by 1 round.
My question: is this spell overpowered at 5th level, or does it need to be an even higher-level spell to be balanced? If cast outside, you would just need to make a melee spell attack against an enemy and you could teleport it 200 feet into the air. Unless the creature has feather falling or some kind of flying capability, it will plummet to the ground, taking 20d6 points of damage. Or you could push any creature into the Astral plane by touching it, teleporting it out of range, and then stepping into its space.
Compare with Plane Shift, which is a 7th-level spell. Fleeting Journey is essentially Plane Shift with a delay of 1 round and only the Astral Plane as the target, instead of being able to choose any plane of existence.
Also compare with Banishment, which is a 4th-level spell. Fleeting Journey is like Banishment with a delay of 1 round, fixed to the Astral Plane, no concentration requirement, and the ability to permanently banish any creature, as opposed to only creatures not native to the current plane.