The Krogan

Krogan:

The krogan are a species of large reptilian bipeds native to the planet Tuchanka, a world known for its harsh environments, scarce resources, and an overabundance of vicious predators. The krogan managed to not only survive on their unforgiving homeworld but actually thrived in the extreme conditions. Unfortunately, as krogan society became more technologically advanced, so did their weaponry. The end result is that they destroyed their homeworld in a nuclear war that reduced their species into primitive warring tribes.
Ability Score Increase:
A + 4 to your Constitution and a + 2 to your Strength.
Size: Your size is medium
Speed: 30ft.
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Biologically Impervious:

Krogan biology reflects the conditions from where they come. The krogan are armored nearly head to toe in thick, chitinous plates which protect the krogan from the hazards of their homeland. They possess a hump which can store water and nutrients, for the resources in Tuchanka are scarce.
Curiously, the krogan also possess redundant organs; a second set of major organs in case of failure or injury. These traits make krogan exceptionally difficult to kill, but perhaps what makes krogan so dangerous is an adaptation known as "Blood Rage."

Blood Rage:
When you are reduced to 0 hit points but not killed outright, you can choose to not fall unconscious and enter a blood rage instead. When you enter your blood rage, you lose concentration on any powers you are maintaining.
The blood rage lasts for 1 minute. It ends early if you regain hit points or if your turn ends and you haven’t attacked a hostile creature or taken damage since the end of your last turn.
For the duration, you are immune to being charmed or frightened and the only Action you may take is either Attack or Dash. You continue to make death saving throws as normal and damage causes death-saving throw failures. However, no amount of success or failures cause you to stabilize or die until blood rage ends. Additionally, when you would receive a death saving throw success you may, instead, remove a death saving throw failure, or vice versa.
When blood rage ends, if you have four or more death-saving throw failures, you die. Otherwise, you fall unconscious.
Once you use this feature, you can’t use it again until you finish a long rest.
Natural Armor:
When you aren’t wearing armor, your AC is 12 + your Constitution modifier. You can use your natural armor to determine your AC if the armor you wear would leave you with a lower AC. A held shield’s benefits apply as normal while you use your natural armor.
Nutrient Hump:
Your large shoulder humps store fluids and nutrients, enabling you to survive extended periods without food or water. You can go twice as long without food or water before you suffer exhaustion.
Powerful Build:
Your count as one size larger when carrying weight, push, drag or life.
Thick Frontal Plate:
Your frontal plate is a natural weapon, which you can use to make unarmed strikes. If you hit with it, you deal bludgeoning damage equal to 1d6 + your Constitution modifier, instead of the damage normal for an unarmed strike.

Toughness:
Your hit point maximum increases by 1, and it increases by 1 every time you gain a level.
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Variants: Tank Bred:

Tank-bred krogan were developed by the warlord Okeer, who was originally investigating the genophage. However, Okeer gradually became obsessed with his work and realized that surviving the genophage had become the only benchmark for a good krogan, which was weakening the species as a whole. He decided to produce a genetically pure, superior krogan—a super soldier—and poured all his efforts into his experiments, even seeking help from the Collectors. As a tank-bred krogan, you may be a prototype from Okeer’s research or developed in another lab setting that branched off of Okeer’s research.
If you would like to play a Tankbred Krogan, gain the following traits in addition to all Krogan traits.
Blind Rage:
Whenever you have less than half your hit points remaining and suffer damage to your hit points, you must succeed on a DC 15 Wisdom saving throw or enter a blind rage, immediately losing concentration on any powers you are maintaining. You must also make the saving throw whenever you choose to enter your blood rage.
While in a blind rage, you must use your action and any potential bonus actions or reactions each round to attack the creature nearest to you. If you can make extra attacks as part of the Attack action, you use those extra attacks, moving to attack the next nearest creature after you kill your current target. If you have multiple possible targets, you attack one at random.
You are in a blind range until you die, are incapacitated, or start your turn with no creatures within 24 meters of you that you can see or hear.

Imprinted Enemies:
Your tank imprints have also imparted tactics and knowledge against specific species. Choose two species to be your imprinted enemies.
You have advantage on Intelligence checks to recall information about your imprinted enemies.
The first time on each of your turns that you hit a creature of your imprinted enemies’ species with a weapon attack, you can roll one of the weapon’s damage dice an additional time and add it as extra damage of the weapon’s damage type.

Tank Imprints:
The tank has imparted knowledge into you via imprints. You gain proficiency with one weapon of your choice, one skill of your choice, and one tool of your choice.