Vahn's Disjunction

You point at an medium or smaller skeletal undead within range of the spell. That creature makes a constitution save, on a failure the magic holding it together ends and the bones fall to the ground for the duration of the spell. The undead cannot move or take actions that would require movement, but if the undead is capable of other actions it can still take them (innate spellcasting, etc.).

At higher levels: When you cast this spell using a 3rd spellslot you now select a 10ft radius area and all medium undead within that area must make the save. for every spellslot above 3rd you increase the radius by an additional 10ft. (e.g. 20ft radius using a 4th level spellslot, 30ft radius with a 5th, etc.) Additionally, for every 2 spell levels above 2nd you increase the size of undead affected by the spell (4th level can affect large or smaller undead, 6th can affect huge, 8th can affect gargantuan)