I've noticed a trend towards 10-foot squares in 5e so most dragons should fit in the dungeon just fine. Even with 5-foot squares a dragon can squeeze, and it sucks for them to fight in those conditions, but most dragons would just be like, "eh, I'm a damn dragon, I can take it." The only problem would be 2.5-foot wide passages meant for humanoids to squeeze through, but I see those very rarely in actual adventures. And the Apex Predator who turns Huge and becomes 15x15 might have to squeeze a lot more and would not be able to go down 5-foot passages, but by 17th level there should be ways to work around that, like a friend with teleportation spells, or shrinking spells, or taking the Change Shape feat.
Here are my thoughts on game balance:
If I were going to use dragons in a mixed group with ordinary characters I probably wouldn't allow them until 5th level. At that point, most classes have some cool stuff going on, and while Fly 60 feet is still a great ability, it's no longer game-breaking.
- At low levels, they are clearly overpowered. The racial traits alone are disgustingly good. I just couldn't figure out how to balance flight and non-humanoid type without making dragons seem artificially gimped.
- By upper levels, I think it evens out. When everybody in the party is attacking 4 times per round, flying, slinging meteor swarm, doing 180 points of damage with Assassinate, etc., then having claws and breath weapons and 26 Strength doesn't seem as impressive.
- The Maximum Strength ability is deceptive. It's meant to a) compensate for lack of magic weapons/armor, b) compensate for lack of Fighting Style, Rage, Smite, hunter's mark, etc., and c) siphon off Ability Score Improvements and feat selections by encouraging you to spend them on Strength. So in a way dragons get fewer ASI than other classes because they need to keep bumping their prime stat well past 8th level in order to take maximum advantage of an important class feature.
- Likewise, the natural weapons (2d6) are no better than a greatsword, and most other abilities are impressive-looking but mediocre once you do the math and compare it to what a dedicated warrior or spellcaster would do. Dragons look tough but they are secretly a hybrid class, sacrificing martial prowes for spell-like breath weapon damage.
- The archetypes are a big question mark, balance-wise. I agonized a lot over things like spellcasting progression and the damage of things like cataclysm and tail slap, and in the end, I went with whatever looked like about the same amount of damage as other classes were dishing out, but it is not well-vetted.
An all-dragon party would be super sweet. That is where the multiclassing rules come in. I could totally see someone taking a few levels of dragon and then branching out into fighter, paladin, or sorcerer. Dragon warlock would be fantastic. It would really be a different approach to D&D fantasy than your standard murder-hobo campaign.
So yeah happened across this and I would like to play it, but I have some misgivings.
While my favorite archetype is the Apex Predator, because I like the idea of a huge bruiser of a dragon, it seems a bit weak compared to the other two. It gets slightly higher Strength, assuming you spend pretty much every single ability score increase on Strength. Huge gains it some more hit points, though potentially the Force of Nature might be doing better, since it is more likely to focus on Constitution. It seems like Huge doesn't increase reach, then again neither did Large. But Large increased the damage of the natural attacks, and it seems like Huge should really do the same for their natural attacks, Tail Slap and Mighty Bite. Speaking of Mighty Bite, uh I am not sure it will get used much. Unless you are on a cliff face or tower edge or something. 2d10 damage is nice and all, but not really better than just attacking twice for 2d6+str damage, especially with the str modifier the Apex Predator can get. And the 1d6 per 10 feet will be, maybe, 1d6. Unless you are in a contrived situation where you can fling them off a cliff or tower or something. Basically it is an underwhelming feature. Heavily Armored is of questionable use. On the one hand the class is SUPER MAD and normally wants a 14 Dexterity for max AC, and this feature can allow you to safely dump Dexterity, but not too far because of the importance of Dexterity Saves. But really unless the Dragon has less than 14 Dex this does NOTHING. Honestly I like the concept of the Archetype, but a lot of it is underwhelming until 13th level. Also there would be some questions on if it can attack anything within 5ft of it once it gets reach, but it does keep the 5ft reach claws so that ends up not really mattering. Another thing, it looks like this archetype is the only one without a 3rd save proficiency?
The Force of Nature is interesting for a Breath Weapon focused build, and would probably not max Strength, and thus lose the use of an entire very primary class feature, just so they can jack the save DC up with higher Constitution. This will also likely end up giving them more hit points than the other two builds. But what happens if you use more than one Breath Weapon in an encounter? Since Devastation gives you a reaction elemental aura thing when you breathe that lasts for a minute. Not really much to say about this one, it is focused on improving the Breath Weapon and it does that.
The Great Serpent seems to turn it into a Warlock, using a Sorcerer spell list. This uh I am not sure how powerful it is. That seems potentially broken, on top of the actual dragon class. Then again if all you go for is blasting it probably doesn't do much more than the actual breath weapon. It is fairly straightforward and strong, but I am unsure if it is too powerful. If you just use all your breath weapons to cast spells it might be more powerful than the warlock class, and that is not counting everything else the actual dragon class gets. Also just how broken is Animal Form? Guess they lose spellcasting? Except they don't really do spells except with their innate dragon breath to spell thing. Lose out on that sweet strength, except that really this build is unlikely to focus on strength. Where the Apex Predator is probably going to use all its ability score increases on increasing strength, with maybe a single spare feat, or two, on either increasing Constitution or actually gaining a feat. The Force of Nature is probably going to spend a couple attribute increases on getting 20 Constitution, maybe some Strength for when out of Breath Weapons, but really wants to focus on that Breath Weapon DC. The Great Serpent is going to want to spend a couple attribute increases on getting to 20 Charisma for the DCs of their innate spellcasting.
For the class as a whole, I like a lot of it, especially getting Unarmored Defense based off the increasing Strength, though it ends up maxing out at 20 anyways, except for the 28 Strength Apex Predator I guess. Which is the same as a 20 Wisdom 20 Dexterity Monk, but a Barbarian can get higher, if they put enough into Dexterity, a Fighter can do better, a Wizard can do better. A lot can do better. The Fighter is going to be having 20+ AC, probably more than 21 by 17th level, and doing four 2d6+str attacks with possible magic weapon bonuses, or extra fire or something with a named magic weapon, similar hp to the Dragon, and whatever they get from their archetype. Admittedly the Dragon does get 3/short rest Breath Weapons. But depending on what archetype the Fighter gets who knows what else they could pull off. Speaking of magic weapons, is there anything that lets the dragon overcome Non-Magical Weapon Resistance? Monks get it eventually and the other actual weapon using classes can get magic weapons. But the Dragon, especially the Apex Predator archetype Dragon, is kind of in trouble when facing something resistant or immune to non magical weapons, and their breath weapon type.
The Dragon is now the character build with the fewest skills. Some races get a bonus skill or more, but not all. All backgrounds, except this new Wyrmling, get 2 skill proficiencies. And all classes get at least 2 class skills, which the Dragon class does get. The class is also fairly MAD. It wants Strength, a lot of strength if you want to actually make use of the class feature that can get your max strength up. It wants Constitution, not just for hit points but also, for the Breath Weapon DC. And it wants Charisma for the Frightful Presence DC. It doesn't get any more ability score increases than any other class, it has its own special feats it might want, and there are feats in the PHB that it will want. It will also want 14 Dexterity, unless Apex Predator, for as much AC as possible.