Scourges are those marshals that have embraced one simple truth: it is better to be feared than loved. They strike fear into the hearts of their enemies, but also their allies. Harsh disciplinarians, they are not afraid to harm or even break those they fight alongside in order to build them back up into something better, and know that a well-placed and credible threat will often accomplish more than an inspiring speech, especially if others know you are willing to back it up.
When you select this archetype at 3rd level you can lambast an allied creature within your Commanding Presence with harsh commands and even threats, no action required, dealing 2d6 psychic damage to them. They gain an expertise die on all attack rolls, saving throws, and ability checks until the start of your next turn. You also gain proficiency with Intimidation. If you are already proficient you gain an expertise die instead.
At 7th level your reputation for harshness extends from your allies to your enemies. When you strike an enemy with a melee weapon attack, you can force them to make a Wisdom saving throw with a DC equal to 8 + your proficiency bonus + your charisma modifier. On a failure, they are frightened of you until the end of your next turn. You can do so a number of times equal to your proficiency bonus and regain all expended uses when you finish a short or long rest.
At 11th level if a creature in your Commanding Presence fails an attack roll or saving throw, you can use your reaction to make an Intimidation check, using the result in place of the triggering attack or save and possibly changing the result. Once you have used this ability on a particular creature, you cannot target that creature again until they finish a short or long rest.
At level 15 you can choose to increase the damage of your Threatening Presence by 1d6. If you do so, the target is also immune to fear for the duration, and if they are currently frightened that condition immediately ends for them.
At 18th level if an allied creature within your Commanding Presence that can see or hear you would be reduced to 0 hit points but not killed outright, you can use your reaction to instill in them a fear greater than death. They instead drop to 1 hit point, they are immune to damage until the end of their next turn (though they must still make a Constitution saving throw or die if they would take massive damage without this immunity), and they have advantage on attack rolls until the end of their next turn. However, they are also frightened of you for the next minute. You cannot use any spell or ability to remove this frightened condition, though other creatures can, and if a targetted creature is normally immune to fear they lose that immunity for the duration. This also still counts as being reduced to 0 hit points for the purposes of gaining fatigue or strife at the end of combat. Once you have done so, you cannot do so again until you finish a short or long rest.