I like to make up spells. Take this one I just generated with some story cubes.
Banished Mimicry.
Level 2 Abjuration spell. Casting time: 1 action. Duration: 1 round. Range: Touch. Somatic.
Touch the target as you cast this spell. The target may make a Charisma saving throw. On success, the target is immune for 1d4 days. On a failure, they vanish into a pocket dimension. In their place stands an identical mimic, who can convincingly sound and act just like the target. The mimic will obey your command, acting as a Friend, and has 1 HP. The spell ends if it is reduced to 0 HP and the mimic disappears, replaced by the original target.
If cast at level 4, duration increases to 1 minute. If cast at level 6, the duration increases to 1 hour. If cast at level 8, the duration increases to 1 day and the mimic has 3d8 HP. If cast at level 9, the duration is “until dispelled” and the mimic has 12d8 HP.
I mean, that’s pretty epic, right? You can make a whole adventure around rescuing someone from that spell.
But it’s also really kind of powerful. A party of enough wizards and they’ll have a small army of non-necrotic thralls running around for them. (To that I say, does that really matter?) Some would be concerned about giving their players a tool like this.
There’s a way to curb how often it’s used though – without just banning it at your table!
See that required “Somatic” tag? Just tack on a “Material: 1 black lotus petal which is consumed by the spell.” Then who cares if this is even a level 1 spell? You control the market for black lotus petals!
Your wizard will be excitedly scouring the world for helpful flora. Hey, it works for Identify and Revivify.