Anti-Transmogrification

If all magic is math, transmutation is multiplication. Combining two ideas, the original and the new, into one greater being. And if that's true, like all math, there must be an inverse, a division.

Choose one creature or object that you can touch, this spell allows you to reach into the target's very being to find who or what it was originally. If the target has previously come under the effect of a True Polymorph spell, a Reincarnate spell or something with similar effects, the target's original form is brought out as the transmutation is undone.

If the target is unwilling, it may make a charisma saving throw against your spell save DC using its current or original charisma(its choice). If the target is currently an object or something else that does not have its own will, the original form of the target may be the one that is unwilling.

The undoing of such powerful spell does have unpredictable side effects, as you might not fully understand what the original equation was to be able to divide the correct ideas. Roll 1d10 and consult the table below for unpredictable side effects, additionally, if the target's original form is a creature it takes a −4 penalty to all attack rolls, saving throws, and ability checks. Every time the target finishes a long rest, the penalty is reduced by 1 until it disappears.

Unpredictable effects: