Does a caster under the effect of a True Polymorph spell retain their class levels?

Question

The true polymorph spell specifies that:

The target's game statistics, including mental ability scores, are replaced by the statistics of its new form ... The creature is limited in the actions it can perform by the nature of its new form, and it can't speak, cast spells, or take any other action that requires hands or speech, unless its new form is capable of such actions.

So let's take the example of a level 20 Sorcerer who has permanently True Polymorphed himself into a Planetar Angel.

The sorcerer's game statistics are replaced by those of the new form. Does this include class levels? The angel's form doesn't limit the physical ability to use spellcasting, but does the sorcerer retain their class-given spellcasting ability?

The wording of the spell seems to imply the caster is still able to cast their spells, as long as the new form is physically capable of performing the required components.

How about a dragon? They are capable of verbal and somatic components, which are the only requirements for spell usage.

Answer 1

Well, you definitely retain your class levels. If someone casts Dispel Magic on you, you'll become a level 20 Sorcerer.

However, True Polymorph does not allow you to use your class features (including the Spellcasting class feature). Compare it to the Druid's Wild Shape ability, or the Shapechange spell, both of which include this paragraph:

You retain the benefit of any features from your class, race, or other source and can use them if your new form is physically capable of doing so. However, you can't use any of your special senses, such as darkvision, unless your new form also has that sense.

Additionally, neither Wild Shape or Shapechange include the phrase "The creature is limited in the actions it can perform by the nature of its new form" that True Polymorph does. It seems clear that True Polymorph restricts you to doing things your new form is inherently capable of doing, whereas Wild Shape and Shapechange allow you to do anything you're normally capable of as long as your new form is physically able to do it.

More intuitively, True Polymorph has an offensive use written in to it. The classic "turn your opponent into a frog" move doesn't really mean much if they become a powerful spellcasting frog wizard, or a stealthy sneak-attacking frog ninja. In some cases, it might even be a boost.

Answer 2

I arrive to basically the same conclusion as Miniman, albeit perhaps for different reasons, so I'll venture a response.

As has already been observed, the spell states:

The target's game statistics, including mental ability scores, are replaced by the statistics of its new form.

The spell provides no language providing an exception to the above statement. For instance, the spell later states:

The creature is limited in the actions it can perform by the nature of its new form

If that creature has spellcasting actions, the target of a True Polymorph may perform exactly those spellcasting actions, as it is the case that those game statistics have replaced the target's statistics.

The remaining text doesn't provide an exception to the preceding text, but further restricts speech and other actions not possible with the new form.

...and it can't speak, cast spells, or take any other action that requires hands or speech, unless its new form is capable of such actions.

The very last statement reinforces the idea that, provided the new form can cast particular spells, the Polymorphed creature may also cast the same spells, and it does so without any verbiage restoring the creature's original spellcasting stats to herself.

In summary, while it might be argued that the last phrase implies the target might retain some spellcasting ability, the first phrase quite directly states that the target of the spell retains none of her original statistics (naturally, barring the termination of the spell), and further loses any speech or capability the new form is not capable of. I think the suspected implication in the last sentence is not strong enough to overturn rules clearly stated.