Is this homebrew terran race balanced?

Question

Is the following homebrew race balanced?

---

Terran

Ability score increase:

+4 to Constitution but -2 to Dexterity

Age:

Terrans live 300 years.

Size:

Large. You are 14 feet tall and weight 700 pounds.

Speed:

Your base walking speed is 15 feet.

Natural armor:

When you aren't wearing armor, your AC is 17 + your Dexterity modifier.

Damage resistances:

You are resistant to acid damage.

Brittle:

You take 50% more fall damage.

Sight:

You cannot see more than 10 feet, and have disadvantage on Wisdom (Perception) checks that rely on sight. You have tremorsense to 60 feet.

Innate Spellcasting:

You know the thaumaturgy cantrip.
At level 20, you can cast earthquake using this trait once per week.

Answer 1

No

This race's design is characterized by massive, overpowered bonuses, offset with unreasonable penalties which in some cases can be trivially ignored by some character builds. This doesn't match up with the standard, carefully-balanced way races are designed in this edition of the game.

+4 to one ability score is too high. A player will just select a character who does not make heavy use of Dexterity. D&D 5th edition races generally don't have penalties to ability scores. Most D&D races have +2 to one ability score and +1 to one other.

17 base AC from natural armor strongly favours anyone who plays a character who ordinarily wears no armour, such as spellcasters and light-armour classes.

Tremorsense is awkward in 5th edition. You can "detect and pinpoint the origins of vibrations", but can you "see" normally at that range? If you can't, you're practically blind; if you can, then the limits on its normal sight are not major if the character spends a lot of time in dungeons where most enemies are within 60 feet and do not fly. Disadvantage to Perception is bad for any adventurer, although if you can "see" within tremorsense range, you don't really have disadvantage in short range. You also have the awkward situation that in a large room, your character can't "see" far away enemies, but your player obviously knows where they are.

A speed of 15 feet is too slow for this edition of the game. +50% fall damage is another weakness, and my concern here is that it's intentionally adding major drawbacks in order to "pay" for overpowered abilities, which isn't how D&D 5th edition race design tends to work.

Large size will cause problems fitting into standard dungeons, which often contain 5 feet wide areas designed for creatures of a smaller size, requiring you to Squeeze, which places you at a disadvantage (although combat tends to take place in more open rooms than this). On the other hand, you can block a 2x2 square area and your attacks can hit the 12 squares adjacent to you, not just 8.

It's rare for a race to acquire an ability at level 20. Most characters will not do a lot of adventuring at that level, either because the character retires (or is killed, or the campaign ends, etc) or because the group stops adventuring upon reaching level 20.

Answer 2

No, Large is a big deal

The Constitution bonus is really rather high, and the Dexterity defecit is fairly negligible when compared to the natural armor. I'd do a +3 Con, -1 Dex, -1 Cha to make it a little more rounded.

Do NOT mess around with larger sizes. It has major implications that even the devs don't want to touch. You can borrow the Goliath's size option, which simply makes them lift as though they were larger.

Speed of 15 is a major problem. The party will not have a good time trying to drag you around from place to place, especially if you're too heavy for a horse.

Natural Armor is a bit too high, unless you were trying to make this thing not wear armor.

Acid resistance isn't too bad. Resistances are rare among PC races, but not unheard of.

Brittle is not very good, due to fall damage being very rare, and it doesn't quite describe how the 50% works. Rounded up or down?

The Sight issue will keep them from being a spellcaster without additional information. Most spells rely on sight, and a sight of 10 feet...well, you get the idea.

Innate spellcasting is mostly okay. Earthquake is a nice spell, but likely nobody will ever see it as it's a level 20 requirement. I'd recommend lowering the Earthquake requirement, replacing the Earthquake with other low level spells, like with the Tiefling. Thunderwave, Earth Tremor, Meld Into stone, stuff like that.

The main concern with this thing (besides size) is that no class really benefits from being a Terran.

Warrior classes are valued because of their armor benefits and versatility, where this class already grants you the equivalent of heavy armor and hurts versatility (with no eyesight and speed).

Spellcasters and ranged fighters wouldn't be able to fight or use magic without a LOT of game breaking.

Rogues would be far too slow with poor stats.

Natural armor doesn't stack with unarmored defenses, which limits how effective choosing a barbarian or monk would be.

MAYBE I'd play a melee warlock, if only because these things are indestructible, and I can just cherry pick spells that center on me or use melee attacks. But that character would be crazy strong.