When the Assassins hits an enemy with a Melee Weapon Attack, make a Constitution DC 10 check. If its failed, the enemy is stunned until its next turn. Enemies immune to the Poisoned condition can't be stunned.

As an action, the Priest blesses an ally it can see linking their souls together. While the priest isn't unconscious or dead, that ally as advantage on weapon attack rolls and it gains Temporary HP equal to its maximum HP. If the priest is killed while linked to another creature, that creature also dies.

As an action, the Captain can mark an enemy it sees. All its allies deal +3 damage to that enemy. This effects lasts until the Captain marks another enemy or the Captain is unconscious or dead.

As an action, the Champion activates its Aura. Himself and all its allies in a 10 ft range gain 20 temporary hit points. If an ally moves more than 10 ft away from the Champion it loses its temporary hit points and can't gain them back. If the Champion is unconscious or dead, all the temporary hits points provided by his Aura are removed.

As an action an Archer can Overwatch. Until its next turn, if the Archer sees an enemy moving in a space without cover, it can use its reaction to make all ranged weapon attacks it could make as an attack.

You can apply this archetypes to any monster - like an Orc, Goblin, Gnoll etc. The main philosophy is allowing enchancing the tactical aspect of combat by having features that reward killing certain enemies and by slimming down DM's book-keeping. Use common sense, since it's not meant to be 'balanced' or 'fair'. Feel free to mix and match any Archetype Features. For example a Priest could have the 'Riding Beast' feature if you want an Orc Shaman riding a Dire Wolf. This document is heavily inspired by X-Com 2.

Raging Attack When the Berserker takes the Attack action, before determining its targets it can move up to 30 ft. If it moves at least 10 ft straight, until the end of the turn any attack that hits is considered a critical hit.

Staff of Fire Breath As an action the Alchemist can produce a thin sheet of flames shoots forth from his staff. Each creature in a 15-foot cone must make a DC 13 Dexterity saving throw. A creature takes 3d6 fire damage on a failed save, or half as much damage on a successful one. The fire ignites any flammable objects in the area that aren't being worn or carried.

Wildfire Bomb As an action the Alchemist throws a bomb in a point it can sees in 30 ft. For the next 10 minutes, the bomb fills with fire a 5-foot cube. Any creature in the fire's space when you throw the bomb must succeed on a DC 13 Dexterity saving throw or take 1d8 fire damage. A creature must also make the saving throw when it moves into the bonfire's space for the first time on a turn or ends its turn there. An Alchemist has 5 Wildfire Bombs.

Raise Dead As an action, the Necromancer can target a dead humanoid creature with its corpse intact. It instantly raises as a Zombie without Undead Fortitude feature. The Zombie acts at the end of the Necromancer's turns. A Necromancer can have only one Zombie raised at a time.

Mindspin As an action, the Necromancer casts randomly one of these spells (Roll 1d6): Cause Fear (1-2), Crown of Madness (3-4), Dissonant Whispers (5-6).

Toll the Dead As an action, the Necromancer casts the cantrip Toll the Dead.

Riding Beast The Rider rides a beast that is one size larger than it. The beast has AC 13 (Natural armor or leather barding), double the amount of HP of the Rider and allows to move at double the speed. If the beast isn't being mounted, it can make a single attack that deals damage equal to the weapon melee attack of the Rider. The beast can also be a flying one but, as the flying mount is more fragile, any time the Rider takes damage it must make a Strenght saving check with a DC equal to 10 or half the damage taken, whichever number is higher or else fall from the mount.

Mounted Charge When the Rider takes the Attack action, before determining its targets it can move up to 30 ft. If it moves at least 10 ft straight, that target must succeed on a Strength saving throw DC 13 or be knocked prone.

Dragonfire Bomb As an action the Juggernaut thros a bomb in a point it can sees in 30 ft. For the next 10 minutes, the bomb fills with fire a 15-foot cube. Any creature in the fire's space when you throw the bomb must succeed on a DC 13 Dexterity saving throw or take 3d8 fire damage. A creature must also make the saving throw when it moves into the bonfire's space for the first time on a turn or ends its turn there. A Juggernaut has 3 Dragonfire Bombs.

Frightful Sight Any creature that moves in any adjacent square to the Juggernaut, starts its turn there or makes a Ranged Attack against it must make a DC 10 Wisdom Saving Throw or become frightened until its next turn.

Weak Mind A Juggernaut has a Wisdom Saving Throw bonus equal to -10.

Sentinel When a creature within 5 feet of the Lancer makes an attack against a target other than it, the Lancer can make a melee weapon attack against that creature.

Minor Illusion As an action, the Spellcaster casts the cantrip Minor Illusion.

Bag of Tricks As an action, the Spellcaster casts randomly one of these spells (Roll 1d6): Fog Cloud (1-2), Invisibility (3-4), Web (5-6).

Phantasmal Clone As an action, the Spellcaster can target one of its allies that he can see and create next to him an illusion identical to it. The illusion has its stats except it has 1 HP. The Illusion acts at the end of the Spellcaster's turn. A Spellcaster can have only one Illusion created at a time.