Serial Killer

A killer who strikes from the shadows and spreads fear throughout a community. Serial killers often kill either for pleasure or for notoriety. Serial Killers are distinct from Assassins, for while Assassins are professionals hired by clients and who expect payment for their services, Serial Killers kill for no one but themselves and their own desires. 

Many Serial Killers are motivated by vengeance, but seldom limits their revenge to a single target, blaming an entire demographic for their misfortune. Others simply gets a sick pleasure in the act of killing and do it for fun. While others see themselves as judges of the wicked and kill only those they deem deserving.

Favoured Victim

When you choose this archetype at 3rd level, you gain a favorite type of victim, this can be any type of humanoid, a specific gender, an occupation or other factor that sets them apart. For example, Jack the Ripper targeted female prostitutes, which would be his favoured victim.

You have advantage on checks to track or spot your favored victim and they get disadvantage on rolls to spot you or discern your murderous intentions.

You also have a +2 bonus to damage with weapon attacks made against your favored victim, which increases to +3 at 6th level, and +4 at 14th level.

Murder

Starting at 3rd level, when attacking a suprised target, you may launch a killing blow using an action, if this attack hits, it is always a critical hit, furthermore, a humanoid target that takes damage from a killing blow must take a Constitution saving throw with a DC equal to 8+your proficiency modifier+ your intelligence modifier, on a failure they are instantly killed. If the attack misses or the saving throw succeededs, the Serial Killer cannot use a killing blow again on the same target until at least 24 hours has passed.

Frightning Appearance

Starting at 9th level, whenever a you make an attack against a foe that is unaware of your presence, any number of creatures of your choice within 30 feet of you must make a Wisdom Saving throw with a DC equal to 8+your Intimidation Proficiency+ your Charisma modifier, on a failure they become Frightened. Frightened creatures may attempt a Wisdom saving throw at the end of their turn to.end the effect. 

Quiet Death

At 13th level, whenever you kill creature using Murder during a surprise round, you can also make a Stealth check, opposed by Perception checks of those in the vicinity to prevent them from identifying them as the assailant. If successful, those nearby might not even notice that the target is dead for a few moments, allowing you to avoid detection.

Grisly Murder

Starting at 17th level, whenever you kill a creature using the Murder ability, all who witness the victim's corpse suffer the effects of the Nightmare spell during their next long rest.