Is this homebrew 'Outsider' race balanced?

Question

I am currently editing a homebrew race that I have created, and after a good few versions, I believe I am coming to some semblance of a decent homebrew race. However, I fear that it may be unbalanced in places.

Is the following race (and and are its subraces) balanced, and if not, what changes could be made in order to make it so?

My main focus appears to be the Fight or Flight mechanic provided to the Gemstone subrace. Playtests have come back mostly positive, however I am worried it may be a little too much for the one subrace.

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Outsider Traits

Your eldritch heritage manifests in a variety of ways that are consistent with your kin.

Ability Score Increase. Your Strength score increases by 2.

Speed. Your base walking speed is 30 feet.

Natural Cunning. Being common with deceit, an Outsider is resistant to tricks of an arcane nature. You have advantage on saving throws against Charm spells and cannot be put to sleep by magic.

Claws. You are proficient at using the large claws you have as weapons. They deal 1d4 slashing damage.

Darkvision. Accustomed to life underground, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. An Outsider retains the ability to distinguish color and detail under these conditions.

Languages. You can speak, read, and write Common and one other language of your choice.

Doppelganger Outsider

Outsiders who have chosen to hide in plain sight rather than in the shadows. A Doppelganger Outsider's flesh is paler than that of their kin, their eyes being smaller and their limbs being more anatomically similar to other human-sized creatures. Because of this, they are often shorter than their Gemstone brethren.

Ability Score Increase. Your Charisma is increased by 1.

Change Shape. As an action, you can transform your appearance or revert to your natural form. You can’t duplicate the appearance of a creature you’ve never seen, and you revert to your natural form if you die. You decide what you look like, including your height, weight, facial features, the sound of your voice, coloration, hair length, sex, and any other distinguishing characteristics. You can make yourself appear as a member of another race, though none of your game statistics change. You also can’t appear as a creature of a different size than you, and your basic shape stays the same; if you’re bipedal, you can’t use this trait to become quadrupedal, for instance. Your clothing and other equipment don’t change in appearance, size, or shape to match your new form, requiring you to keep a few extra outfits on hand to make the most compelling disguise possible. Your true form is revealed if you fall unconscious.

Outsider Tricks. While the change shape ability is active, creatures have a disadvantage on checks trying to see through your disguise.

Gemstone Outsider

Outsiders whose ancestors have remained in the caves of their origin. A Gemstone Outsider's flesh is hardened, almost like chitin. Their eyes are indistinguishable from gemstones, aside from the fact they glow with a deep, arcane energy.

Ability Score Increase. Your Dexterity is increased by 1. Your Intelligence is decreased by 1.

Psionic Shift. At first level, you can cast misty step once per long rest. At third level, you can cast blink once per long rest.

Fight or Flight. Upon reaching 0 hit points or below, roll a Constitution saving throw equal to the amount of damage taken by the attack. If you succeed, you return to your most primal instincts, and lash out like a wild beast. You gain temporary hit points equal to half your maximum hit points, rounded down, and do not fall unconscious while you have these hit points. You must use your turns to attack any and all hostile creatures, starting with the nearest, in a 60ft radius centered on you. You cannot move further away from a hostile creature within this range, unless you are moving towards another hostile creature. This lasts for a number of rounds equal to your proficiency bonus rounded down, after which you fall unconscious and lose any remaining temporary hit points. This effect cannot be used more than once until you take a long rest.

Answer 1

As written, this race's abilities do not align with the official races. I have tried to provide some guidance below.

First: Special Abilities:

Gemstone Outsider: Fight or Flight

This is substantially better than the Half-Orc's Relentless Endurance.

Fight or Flight. Upon reaching 0 hit points or below, roll a Constitution saving throw equal to the amount of damage taken by the attack.

The problem is that this could be a very high or very low number. Damage rolls are often low individually (eg an animal with multi-attack), or extremely high (damage from a spell or high-powered trap). The ability to use this feature is very unpredictable.

You gain temporary hit points equal to half your maximum hit points, rounded > down, and do not fall unconscious while you have these hit points.

Compare, again, to the half-orc ability that gives you one HP back. Your ability allows the player to continue the combat with a massive amount of HP, giving the rest of the party many turns to react. On the other hand, the half-orc must be extremely careful, and the party must react quickly. Your ability is demonstrably superior, by a wide margin.

My recommendation is to give this race the existing Relentless Endurance feature.

Doppelganger Outsider: Change Shape

This is a true transformation, which is extremely powerful. The first comparable ability is Polymorph, a 4th level spell. However, even this does not allow transformations into other humanoid creatures.

Furthermore, there is no daily limitation on your ability as designed, unlike any other extraordinary racial ability in the PHB. We can make the ability more mundane and unlimited, or more extraordinary and more limited.

Whenever designing features, it is best practice to go off existing content and stick as close to existing rules as possible.

How I would balance Change Shape:

I prefer to keep this first level ability balanced for unlimited uses. Starting characters can use tool proficiencies many times per day without issue. Therefore, I would give this race an ability equivalent to proficiency with Disguise Kit.

Changeable Form The character can innately, and without resources, make any cosmetic changes to their appearance that would be possible with a standard disguise kit, such as hair and skin tone. It takes as much time to change their appearance naturally as to use a disguise kit. Using this ability allows you to add your proficiency bonus to any ability checks you make to create a visual disguise.

This allows them to add their proficiency bonus to their Disguise skill. The "ribbon" is that this is an innate ability that does not require expending a disguise kit. However, it still takes as much time to accomplish.

At third level, the ability to cast Disguise Self once per long or short rest.

At fifth level, a limited version of Polymorph, once per long rest, with the limitations in your original design, would be closer to balanced. This transformation grants the viewer disadvantage on seeing through the disguise.

I don't have a direct ability to compare a true "doppelganger" power to. Polymorph is not normally available to players until 7th level, the limitations bring it more line with what a fifth level character could do.

Determining if this fifth level ability is properly balanced would require playtesting.

Second: Other Abilities

Darkvision ... You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. An Outsider retains the ability to distinguish color and detail under these conditions.

Darkvision specifically prevents seeing color. If you want to add an exception to Darkvision, that should be called out in a separate ability. However, the race already has many good abilities. I recommend reverting to standard Darkvision.

Psionic Shift At first level, you can cast misty step once per long rest. At third level, you can cast blink once per long rest.

As noted in the comments to your post, the standard spell-like ability distribution is a cantrip at 1st, a first-level at 3rd and another at 5th.

I suggest a cantrip at 1st level, such as Mage Hand or Prestidigitation. Misty Step is appropriate at 3rd level.

Blink, on the other hand, is a third-level spell. As designed, you are granting access to this spell as a racial ability before any caster could get it. I recommend selecting an alternative first-level spell for the fifth-level racial ability. I don't know exactly what the story behind this race is, so I cannot make a recommendation.