Champion Decreed Knight

Indomitable (2/Day).  The Elemental Decreed Knight rerolls a failed saving throw.

Survivor.  The Elemental Decreed Knight regain 20 hit points at the start of their turn if it has at least 1 hit point but fewer then half their hit point maximum.

Second Wind (Recharges after a short or long rest).  As a bonus action, the Elemental Decreed Knight can regain 40 hit points.

Powerful Strike.  When the Champion Decreed Knight hits a melee attack against a creature they can add an additional 4d6 damage (included in attack) of the weapons type to the damage roll.

Behead.  When the Champion Decreed Knight rolls a natural 20 against a creature no more then one size larger then the Champion Decreed Knight, the creature must have a defined neck and need its head to survive, and the creature is below half it maximum HP, then the attack automatically kills the creature by beheading it.

Decreed Knight Specialty.  The Elemental Decreed Knight has a given rank that is a show of power that they have achieve, with the higher rank having the features of all the ranks below it.
The highest Black Armored has all the ability of Black, Purple, Blue, and Red.  Purple armored has the ability of Purple, Blue , and Red.  Blue armored has the ability of Blue and Red.  Red armored has the ability of Red
Black Armor.
Advantage on all attacks rolls.
Purple Armor. 
Advantage on stealth check even with heavy armor, and they have a sneak attack of 4d6 that follows the Sneak Attack Rules
Blue Armor.
They can give orders and those that follow the order within 60 ft. that follow the order have advantage on what the order was.
Red Armor.
Has the Sentinel Feat

Multiattack.  The Elemental Decreed Knight gets to make three attacks per turn.

Longsword.  Melee Weapon Attack: +12 to hit, reach 5 ft., one target.  Hit: 29 (2d8+6), or 31 (2d10+4d6+6) if using two hands, Slashing damage.

Longbow.  Ranged Weapon Attack:  +11 to hit, Range 150/600 ft., one target.  Hit: 28 (2d8+4d6+5) piercing damage.