True, but sometimes DMs don't play heavy or forget about making concentration checks every time and see more as they can only use those con spells one at a time. But true concentration can easily be broken

Wow. So, you can now use legendary actions and creature spellcasting with this spell.

Only downside is you lose the following: "You retain the benefit of any features from your class, race, or other source and can use them, provided that your new form is physically capable of doing so. "

Doesn't say you lose them, either; and wouldn't loosing a feat that grants proficiencies, for example, be at odds with the retaining proficiencies part of the description?

It says you lose everything except what it says you keep. So it wouldn't and doesn't have to based on how the English language works.

I guess it hinges on how you interpret "game statistics". So you would say that any proficiency a character previouisly acquired from a feat they would lose when they cast this spell, even though the spells description says you keep your proficiencies?

Quote from Captivecreepa >>

correct, this now the most broken spell in DnD

 I think that honor goes to witch bolt. You can cast it at level one, doing high damage on a hit. For every turn after (until you lose concentration) you get an automatic d12 of damage as a bonus action. You can then use your action to either cast a cantrip (like poison spray every round after. The dpr over 3 rounds with a hit rate of 65% would be (8.45 + 10.725 + 10.725)/3, or 9.96 dpr.

Compare this to casting magic missile and poison spray twice, which would be (10.5 + 4.225 + 4.225)/3 or 6.316 dpr.

(one thing to note, if the enemy you cast witch bolt on dies, the spell is over)

So, why do monster stat blocks keep talking about not needing Temp HP to maintain this transformation, when the spell doesn’t care if you have Temp HP?

"When you cast the spell, you gain a number of Temporary Hit Points equal to the Hit Points of the first form into which you shape-shift. These Temporary Hit Points vanish if any remain when the spell ends."

No where does it say that you get new Temp Hit Points when you use the magic action to change forms. You only get Temp HP when you first cast the spell. S don't shape-shift into a badger and then expect to get better HP when you change to a dragon. You're stuck with the Temp HP of a badger. 

That's correct, and kind of why I think this is better balanced than the 2014. Changing into a dragon that could then cast from your wizards prepared spell list was OP, to put it mildly.  So for the duration ... you are another creature ... and then another and another, etc. Keep a deck of options at hand so that you know what traits you might need to take advantage of as the situation changes. 

Forget the infinite HP thread, I think it is pretty clear that you get one set of Temp HP when you cast the spell and that is it. 

Quote from dandelion_msla >>

Adult metallic dragons can use this to turn into archmages, and other humanoids with spell casting now?

 Are there any adult dragons that have spell Shapechange on their spell lists? The bonus action shapechange isn't the same, what it does is listed in the stat blocks :

Change Shape. The dragon magically transforms into any creature that is Medium or Small, while retaining its game statistics (other than its size). This transformation ends if the dragon is reduced to 0 hit points or uses a bonus action to end it.

 OR (from Ancient Copper Dragon 2024 MM):

Shapechange (Beast or Humanoid form only, no Temporary Hit Points gained from the spell, and no Concentration or Temporary Hit Points required to maintain the spell)

Errata is the reason why. Before the Errata. they nerfed it as they did realise it gave the player infinite temp hp basically.

Quote from Jurmondur >>

Quote from Captivecreepa >>

correct, this now the most broken spell in DnD

 I think that honor goes to witch bolt. You can cast it at level one, doing high damage on a hit. For every turn after (until you lose concentration) you get an automatic d12 of damage as a bonus action. You can then use your action to either cast a cantrip (like poison spray every round after. The dpr over 3 rounds with a hit rate of 65% would be (8.45 + 10.725 + 10.725)/3, or 9.96 dpr.

Compare this to casting magic missile and poison spray twice, which would be (10.5 + 4.225 + 4.225)/3 or 6.316 dpr.

(one thing to note, if the enemy you cast witch bolt on dies, the spell is over)

 i agree. I recently cast witch bolt at an adult red dragon using a 5th level spell slot, 5d12 lightning damage a turn. My DPR was 32.5. too high

If you take massive damage/have HP max of 0 and die while concentrating in the form of a planetar, are you instantly revived on Mount Celestia?

Quote from BrogmirOrdruun >>

If you take massive damage/have HP max of 0 and die while concentrating in the form of a planetar, are you instantly revived on Mount Celestia?

Oh, that's a fun one. Personally, if I were DMing, I'd be inclined to say that you do, but very much without any guarantees that anyone around you on Mount Celestia is happy about it.

Quote from Scienceboy1 >>

Quote from Jurmondur >>

Quote from Captivecreepa >>

correct, this now the most broken spell in DnD

 I think that honor goes to witch bolt. You can cast it at level one, doing high damage on a hit. For every turn after (until you lose concentration) you get an automatic d12 of damage as a bonus action. You can then use your action to either cast a cantrip (like poison spray every round after. The dpr over 3 rounds with a hit rate of 65% would be (8.45 + 10.725 + 10.725)/3, or 9.96 dpr.

Compare this to casting magic missile and poison spray twice, which would be (10.5 + 4.225 + 4.225)/3 or 6.316 dpr.

(one thing to note, if the enemy you cast witch bolt on dies, the spell is over)

 i agree. I recently cast witch bolt at an adult red dragon using a 5th level spell slot, 5d12 lightning damage a turn. My DPR was 32.5. too high

Upcasting the witch bolt only increases the damage on the first cast, and does not increase the subsequent damage dice.