Centurion

Many philosophers have asked the question "Quis Costodiet Ipsos Custodies?" – Who will guard the guards? However, it is not fellow philosophers who answer this question, it is instead the brave Centurion, who answers "I". Having undergone highly disciplined training of both body and mind, this highly adaptable subset of fighter is not only feared when fought alone, but if allowed to fight with allies, they become unstoppable, using powerful tactics and even more powerful words to boost entire armies past their normal limits. 

~Cognomen~

Beginning when you choose this archetype at 3rd level, you may choose a cognomen which tells all who hear it of your impressive qualities.

At 5th level, and again at 7th level, more cognomens become available.

Aculeo

Meaning "Prickly" and "Unfriendly". Lose 2 Charisma, but gain advantage on attacks of opportunity.

Brutus

Meaning "Brutish" and "Stupid". Lose 3 Intelligence and 3 Wisdom, but gain 4 Strength, even if it would put your Strength past 20. If you know more than one language, you now only know one language.

Caecus

Meaning "Blind". Disadvantage on perception checks, but gain immunity to the blinded and charmed conditions.

Dolabella

Meaning "Hatchet". Gain +2 to hit and +1d4 slashing damage while using an axe.

Fimbria

Meaning "Fringes" and "Edge of clothing". -2 AC, but +2 to hit and +1d6 slashing damage against enemies wearing light armor.

Galeo

Meaning "Helmet". +2 AC while wearing armor, but -2 Intelligence.

Licinus

Meaning "Spiky". Melee attacks against you cause the attacker to take 1d4+1 piercing damage.

Lurco

Meaning "Gluttonous" and "Greedy". Gain +4 Constitution, even if it would put Consitution past 20, but lose 10 speed.

Malleolus

Meaning "Hammer". Gain proficiency with hammers and +1d8 bludgeoning damage while using a hammer.

If you are already proficient with hammers, gain twice proficiency.

Nerva

Meaning "Vigorous". Gain 3 in either Dexterity or Constitution, and increase your maximum Constitution score by 2.

Poplicola

Meaning "Friend of the People". Gain 2 Charisma and gain advantage on persuasion checks, but gain disadvantage on intimidation checks.

Prisca

Meaning "Very Ancient". Lose 2 Constitution, but gain 2 Intelligence and have advantage on History checks.

Scaevola

Meaning "Left-handed". Gain +4 to hit, but you are no longer allowed to dual wield and gain disadvantage on any ability check involving using your right hand.

Scipio

Meaning "Rod" and "Staff". Gain the ability to learn and cast 4 Wizard cantrips of your choice, but you may only cast each one 2 times per long rest.

Taurus

Meaning "Bull". Gain 3 Strength and 2 Constitution, even if it would put your ability scores past 20, but lose 2 Dexterity and 1 Intelligence.

~Vexillium~

Starting at 7th level, once per short rest, you can lift your battle standard, rallying your allies to battle, and giving all friendly creatures within 60 ft 1d6+Constitution modifier temporary health, and making all melee attacks done by them do an additional 1d6 slashing damage.

~Advanced Tactics~

At 10th level, you can access the true potential of a battle tactic. Twice per short rest, you may select one tactic to follow.

Each tactic not only affects you, but also all friendly creatures within a 15 ft radius around you:

Ciringite Frontem

Meaning "Hold Front". Lose 20 speed, but deal 1d8 slashing damage with melee attacks.

Contendite Vestra Sponte

Meaning "Your Own Effort". Lose 1 AC, but gain 2 reactions and deal 1d6 slashing damage with melee attacks while there are no allies within 5 ft of you.

Affects a 30 ft. radius instead of the usual 15 ft radius.

All effects that rely on allies (Such as the Pack Tactics of a wolf) act as if there are no allies nearby while the caster and/or target are affected by Contendite Vestra Sponte.

Cuneum Formate

Meaning "Form a Wedge". Melee attacks gain +3 to hit, but ranged attacks get -4 to hit.

Iacite Pila

Meaning "Throw Spears". Gain +2 to hit and 1d6 piercing damage with all ranged attacks.

Orbem Formate

Meaning "Form a circle". Wearing heavy armor grants +3 AC, but wearing light or no armor grants +2 to hit with ranged and spell attacks, but -4 AC.

Praecantatio Formate

Meaning "Form Magic". Gain +2 to hit and 1d4 fire damage on spell attacks.

Testudinem Formate

Meaning "Form Tortoise". Gain +2 AC, but lose 10 speed.

If you are wielding a shield, gain +3 AC and lose 15 speed instead

~Cognimus~

Starting at 15th level, your cognomen gets upgraded, and starts affecting allies within 15 ft.

Acerrima Dolabella

Meaning "Sharpest Hatchet". Gain an additional 2 to hit and 1d6 slashing damage while using an axe.

Allies within 15 ft. gain 1d6 slashing damage while you wield an axe.

Acullimus

Meaning "Prickliest" and "Least Friendly". Lose 2 additional Charisma, but gain the ability to make attacks of opportunity on enemies 10ft away.

Allies within 15 ft lose 1 Charisma, but gain +2 to hit when using a reaction.

Ambidextra

Meaning "Ambidextrous" or "Two Right Hands". Lose disadvantage with ability checks involving your right hand and regain the ability to dual-wield. 

Allies within 15 ft. gain +2 to hit when dual-wielding.

Bellator Populi

Meaning "Warrior of the People". Gain advantage on intimidation checks and 2 additional Charisma, but gain disadvantage on persuasion and deception checks.

Allies within 15 ft. gain advantage on intimidation checks.

Brutissimus

Meaning "Most Brutish" and "Stupidest". Lose 2 additional Intelligence and 3 Charisma, but gain 2 additional Strength, even if it would put your Strength score past 20, and deal an additional 1d6 piercing damage on melee attacks.

Allies within 15 ft gain disadvantage on all ability checks involving Intelligence, but gain temporary health equal to your Strength modifier.

Allies may only gain temporary health from Brutissimus once per day.

Caeccimus

Meaning "Blindest". Gain disadvantage on any check relying on seeing, but gain 60ft of Blindsight and Tremorsense.

Allies within 15 ft. subtract your Wisdom modifier from perception checks, but gain immunity to the blinded condition.

Durrimo Galeo

Meaning "Toughest Helmet". Gain immunity to critical hits.

Allies within 15 ft gain 1 AC.

Dux Populi

Meaning "Leader of the People". Gain 1 additional Charisma, but instantly fail all intimidation and deception checks.

Allies within 15 ft. gain +2 to hit and deal an additional 1d6 psychic damage on all melee attacks.

Licinnimus

Meaning "Spikiest". Melee attacks against you cause the attacker to take an additional 1d4+1 piercing damage.

Allies within 15 ft. gain 1 AC.

Lurccimo

Meaning "Greediest" and "Most Gluttonous". Gain an additional 2 Constitution, even if it would put your Constitution past 20, but lose 3 Dexterity.

Allies within 15 ft gain 4 temporary health, but lose 10 speed.

Allies may only get temporary health from Lurccimo once per day.

Maximo Scipio

Meaning "Greatest Staff". Gain the ability to cast Ray of Frost as a bonus action.

Allies within 15 ft. gain +3 to hit with spell attacks.

Maximus Malleolus

Meaning "Biggest Hammer". Hammers deal an additional 1d10 bludgeoning damage and weigh half in your inventory.

Allies within 15 ft. deal 1d4+1 bludgeoning damage while you have a hammer equipped.

Nerrvima

Meaning "Most Vigorous". Gain 3 in whichever stat (Dexterity or Constitution) you did not pick previously.

Allies within 15 ft. may add your Dexterity modifier as temporary health.

Allies may only receive temporary health from Nerrvima once per day.

Optimus

Meaning "Best". Gain 3 in one ability score.

Allies within 20 ft. gain 1 AC, 5 speed, and +1 to hit.

Prisscima

Meaning "Extremely Ancient". Lose 3 Strength, but gain 1 Wisdom and 2 additional Intelligence, even if it would put your Intelligence score past 20.

Allies within 15 ft. may add your Intelligence modifier to any spell's damage.

Scaevollima

Meaning "Very Left-Handed". Gain 1d6 slashing damage to melee attacks and treat all weapons as two-handed, whether they are being two-handed or not, but instantly fail any ability checks involving your right hand.

Allies within 15 ft. gain +2 to hit with weapons in their left hand, but get -2 to hit with weapons in their right hand.

Taurrimus

Meaning "Most Bull-Like". Gain 3 Constitution and 2 Strength, even if it would put your scores past 20, but lose 3 Dexterity, 2 Intelligence, and 3 AC.

Allies within 15 ft. gain 2d6 piercing damage if they have moved toward an enemy this turn, but lose 2 AC.

Tinea

Meaning "Moth". Lose an additional 2 AC, but gain an additional +2 to hit and 1d6 slashing damage against enemies in light armor.

Allies within 15 ft. lose 1 AC but gain 1d4 slashing damage against enemies in light armor.

~Optimus Virtutis~

Meaning "Greatest Power". At 18th level, you become a beacon of strength for your allies and a nightmare for your enemies. 3 times per long rest, all allies within 60 ft regain 1d6+2 health points, and all enemies within 60 ft must make a Dexterity saving throw or become prone.