Agaliarept's Morphic Binding

You throw a handful of specially prepared powder at a target creature and speak an incantation.

Make a ranged spell attack against the target. On a hit, the powder clings to the creature and forms mystical sigils across its exterior. If the creature is a shapechanger and its current form is not its true form, it must succeed a Constitution saving throw at the start of each turn or be forced into its true form.

So long as the sigils remain, the affected creature becomes locked into its current form and no abilities or spells can cause its form to be changed, unless it would cause it to change into its true form if it is not currently in that.

The spell lasts until the target takes ten minutes to fully scrape the powder off itself or it is subject to successful Dispel Magic.

As a Ritual: This spell can only be cast as a ritual if the creature it targets is willing or completely unable to resist for the requisite ten minutes. When cast as a ritual, you may replace the material component with magical inks made from the same components, worth 250gp, which are consumed as you paint the sigils onto your target directly. Upon completion of casting this spell as a ritual, the inked sigils sink into the target creature's skin and become permanent tattoos.

The tattoos made by casting this spell as a ritual resist attempts to remove them by both mundane and magical means and can only be removed through the Wish spell.