There are setting limits to some classes and subclasses. Sometimes it's a race limitation, sometimes a geography limitation.

This campaign makes for new limits of course, both by geography and race. Those will be covered below. I'm putting each class in it's own post, and covering the high points. There may be some limits I've missed for subclasses, of course. The more they publish, the more there are to keep track of. I may not have taken all of them into account.


Edit
I'll fill in some notes regarding possible backgrounds and necessary adjustments below Classes. This is a work in progress, and may be incomplete.
This message was last edited by the GM at 16:02, Wed 01 Sept 2021.

Truthfully, this depends too much on metal and fire metal to mold it, even the exception (Alchemy) is impossible underwater.

This class in any form is not available to Aquatics.

The Aquatic races available for this campaign are just too civilized for Barbarians.

Instruments are too big an core ability of this class, and impossible underwater As such, it's nearly unheard of for Aquatics.

The one exception is a few rare Merfolk women. Sirens, practicing the magic of the College of Glamour. Usually with magic to amplify the range of their voices. They usually know and use a Lyre.

No, you may NOT play a Siren. It is included for completeness and background knowledge.
This message was last edited by the GM at 00:43, Wed 01 Sept 2021.

Some sea elves far to the North might have clerics of Deep Sashelas.

All Tritons worship Poseidon.

Half Tritons and Blessed of Poseidon follow Poseidon, of course.

Most sea elves and all Merfolk follow a druidic path.

Arabic Gensai are more likely to be warlocks serving a Marid than clerics.
This message was last edited by the GM at 16:34, Fri 12 May 2023.

Tritons are never druids. Nor are half breeds or Blessed of Poseidon.

Merfolk, sea elves, and Arabic Gensai maybe druidic. Gensai tend more towards Moon Circle, but might be Coastal. Merfolk and Sea elves tend more towards Coastal, but may be Moon Circle.

Other circles are vanishingly rare, and will probably not be approved, but you can always ask.

Merfolk and sea elves probably would opt for Ranger. They live by hunting, after all.

Tritions and Gensai of all stripes can be most subclasses of Fighter, although Eldritch Knight is more commonly an Arabic choice. Poseidon's followers tend to prefer a divine spell source.

Monks are far to the east, and on the other side not only of the Great Wall, but all those Goblins inhabiting much of Mongolia and all of Siberia.

Don't ask. Really.
This message was last edited by the GM at 16:35, Fri 12 May 2023.

Tritons, half tritons and Blessed of Poseidon opt for  Paladin over ranger, and, often, fighter. Most Oaths are available, but one or two might not fit well. Ask first, just in case.

Sea elves and merfolk may produce the occasional Ancients Oath Paladin.

Sea elves and merfolk live by hunting for the most part. Their warriors are Rangers, not fighters. Many subclasses will work, but some may have issues. Check first just in case.

Trition and Poseidon based gensai are extremely unlikely to opt for ranger, but it's not impossible. It needs to be approved first, however.

First environment is always Coastal for Gensai.
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As the environment is so different undersea than on the surface, I'm imposing certain class ability replacements for Aquatic trained characters from Tasha's. These substitutions are not optional, but meant to replace abilities, such as difficult terrain and tracking boosts.

-Deft Explorer replaces Natural Explorer.
-Favored Foe replaces Favored Enemy.

Aquatic training allows the use of a druidic focus at 2nd level. Surfacers may learn this ability per the training rules in Xanathar's.
This message was last edited by the GM at 01:21, Fri 29 Apr 2022.

Rogues are not my best known class, so I'm just going to say that Tritons and Gensai could, conceivably, be of any subclass. Fell free to ask and I'll check appropriateness for the setting and geography. Some probably won't be allowed for one reason or another.

Merfolk and Sea elves are most likely going to be Scouts.
This message had punctuation tweaked by the GM at 16:37, Fri 12 May 2023.

For the most part, Storm Sorcery is the bloodline of the water born. It is, after all, the arcane equivalent of Poseidon's Domain, the best expression of Elemental Bloodlines, and common to many  Elf types.

All that being said, there are still Merfolk. The Sorcerers they produce are Wildmages. Much like humans, innate magic is rare and uncontrolled with them.
This message was last edited by the GM at 16:38, Fri 12 May 2023.

Tritons, full or half blood, and Blessed of Poseidon already have a Patron: Poseidon. They don't go warlock.

Elves just don't do warlocks, either. They don't need someone to give them arcane magic. It's already in their blood.

The last time Merfolk dabbled in Warlockery, Merrow come into being. Its not impossible, but it's extremely unlikely.

That leaves Humans and Arabic Gensai.

Humans in an undersea setting at low level (under 5th) are exclusively Fathomless. Mind you, this is one of a couple different Primordials, not a single entity, and each one might have different goals. I'll allow one such visiting human player.

Arabic Gensai might well serve a Marid as a Warlock. I'm willing to allow one such.
This message was last edited by the GM at 16:38, Fri 12 May 2023.

Probably not a good idea for anyone. The issue here is the spell book and the inks necessary to update it

That being said, a parchment book, made from aquatic leather, is possible. I'll count it as double weight. Ink is still an issue, so I'll limit this to a gensai with surface training. This pretty much means a half blood triton or an Arabic gensai.

Given the difficulties, I'll limit this, too, to one character.

Keep in mind that updating the book with new spells (other than from level gains) will require some sort of magic or some days on the surface. And storing Ink underwater is probably not possible.
This message was last edited by the GM at 16:39, Fri 12 May 2023.

Any background works for the surface raised, assuming that the background is available by geography or race.

For Aquatic raised characters, the options are fairly narrow, and may need adjustments especially in regards to equipment provided.

None from Saltmarsh work for Aquatics.

Only two from Sword Coast Adventurer's guide really work well for Aquatics:
City Watch works well enough for Tritons, and Inheritor works for anyone.

Most PHB Backgrounds work fairly well, but some may be limited by race. Sailor/Pirate doesn't apply to Aquatics at all, and the only major city is Old Atlantis (which limits Urchin, and, probably, Charlatan). For now things are case by case, as vetting the minutae of each one will take some time. I'll do it as it comes up, for now.