Downfall

NOTE: YOU CANNOT MULTICLASS INTO OR OUT OF FIGHTER WITH THIS SUBCLASS

Once upon a time, three happy birds lived in a warm and lush forest. The birds had no names, though the creatures of the forest would call them Big Bird, Long Bird, and Small Bird. Everyone lived freely and happily together in the peaceful forest. The birds wanted the forest to be safe more than anyone else, that way creatures from the outside could visit and have fun.

It was a warm and sunny afternoon when a stranger visited the peaceful forest. He was a traveler, pioneer, and prophet, but at the same time, he was a nobody. He wanted to enter the forest, but the birds found him suspicious, so they didn't let him in.

The stranger, angered, told the birds as he left: “Soon, a tragedy will befall the forest. It will be tainted with misdeeds and evil, and there will be constant conflict. The tragedies will only stop when a terrible beast appears and devours everything. The sun and moon will shine upon the forest no longer; the forest will never go back to what it was before.

His Gaze

3rd level feature

Big Bird, with its many eyes, decided to watch over the forest for intruders. For Big Bird's eyes could see very far, and see things we cannot see.

You gain proficiency in the Perception skill, and you can add 1d4 to Perception checks based on sight. Additionally, you gain Blindsight up to 30 ft. (This does not stack with the Blind Fighting Style). At 20th level, you also gain Truesight up to 60 ft. and gain proficiency in Wisdom saving throws.

You can bond with a set of heavy armor over an 8 hour ritual where you remain in contact with the armor throughout the ritual. This bonded armor is now considered to be "Under His Gaze". While bonded and wearing this armor, whenever an enemy makes an attack roll against you while within your Blindsight (or Truesight at level 20), they suffer a penalty to the attack roll equal to quarter of your Perception check modifier (rounded up). Bonuses that add dice to the check (Bardic Inspiration, Guidance etc.) do not increase this effect.

You can have only one set of armor Under His Gaze. If you complete the ritual with another set of armor, then the initial armor is no longer considered Under His Gaze.

His Scale

7th level feature

Long Bird weighed the sins of creatures that enter the forest to keep peace. Long Bird's scales could measure every sin, and were fair and just

You gain proficiency in the Insight skill, and can add a 1d4 on all Insight checks to find out lies. At level 20, you gain expertise in the Insight skill.

Additionally you can cast Zone of Truth (DC 8 + your proficiency bonus + your Strength modifier) once a day without any components. When you succeed on an insight check against a deception check a creature that willingly lies to you they become frightened for 1 minute.

His Beak

10th level feature

Small Bird decided to punish the creature's wrongdoings with its beak.

You gain proficiency in the Intimidation skill and can add 1d4 to the Intimidation check. At level 20, this changes to expertise in the Intimidation skill.

As an 8 hour ritual, you can bond with one melee weapon. This weapon loses its Finesse property if it has it, and gains the Heavy property. As part of the Attack action you make with your Bonded weapon, you can make an Intimidation check contested by a Wisdom saving throw from the target of the Attack. If you succeed, the target becomes vulnerable to all damage you deal with that attack. A creature can be affected by this effect only once until Initiative ends.

You can have only at most two Bonded Weapons at a time. Doing the ritual with a third weapon breaks the Bond with the first weapon.

Then Someone Said...

15th level feature

But what if the beast shows up in the middle of the night, when the sky is dark and everyone is asleep?
You emit a constant aura of darkness around you, reaching 10 ft. Creatures within this aura are considered lightly obscured. Additionally, when they enter the aura for the first time, they must make a Charisma saving throw (DC: 8 + your proficiency bonus + your Strength modifier) or fall asleep as if under the Sleep spell. If they pass the save, they become immune to the Sleep effect for 24 hours.

But what if the scale doesn't tip in either direction someday?
When you attack a creature of a Neutral alignment that has not taken any harmful actions against you, you must make a Wisdom saving throw (DC equal to the creature's level or CR) or lose the attack. Once the creature takes a harmful action against you, you no longer need to make the saving throw.

But your beak is so small, no one would find it hurtful.
Whenever you deal damage to a creature that is at full health, you deal half your total damage.

Worry

18th level feature

Worried, Big Bird burned all of its feathers to make an everlasting lamp. Now the creatures of the forest were under Big Bird's constant watch, day and night. 
While inside your aura of darkness, allies gain blindsight equal to 10 ft. Additionally, when wearing your Bonded Armor, you gain immunity to Radiant and Necrotic damage from sources you can see or sense within your Blindsight.

Worried, Long Bird made a scale that always tipped to one side. That way every judgement would yield a clear verdict.
When you hit a melee weapon attack, you deal an additional 2d8 damage. This damage is Radiant if the target is evil, Fire if the target is neutral and Necrotic if the target is good.

Worried, Small Bird tore its mouth wide so it could swallow any creature in one bite.
When you use your Action Surge feature to take the Attack action with your Bonded Weapon, you may forgo making additional attacks. For each attack you forgo, you may add all the damage rolls of that attack to the initial attack's damage. You do not add any flat bonuses to the initial damage.