Roguish Archetype - Deathstalker of Bhaal
Ruthless servants of the dead Lord of Murder, these worshippers were scattered after Bhaal's untimely death, spreading across the realms. Only the truly zealous and dedicated can become a deathstalker, but in return they are granted fragments of their god's powers, able to paralyze their foes, incite murderous rages, and even return themselves from death - so long as they continue to kill.
Many deathstalkers believe that each murder in Bhaal's name brings him one step closer to returning, and so it isn't unheard of for these rogues to go 'undercover' with adventurers, using their party as cover for their misdeeds. Sometimes they will even work to corrupt the party from the inside, turning them steadily from the path of righteousness to that of murder.
Death Attack
Deathstalkers learn to twist their blades in devious and deadly ways. From 3rd level on your turn you can use your bonus action to prepare a Death Attack against a foe you can see that is a viable target for your Sneak Attack. If you then hit the target with an attack that turn, the creature must make a constitution saving throw (DC=8 + your proficiency bonus + your dexterity modifier) or be Incapacitated until the start of your next turn.
Death Attack can be used a number of times equal to 1/2 your Sneak Attack dice (rounded up), refreshing on a short or long rest.
In addition, if your sneak attack reduces a creature to 0hp, they are not granted death saving throws, and instead die immediately. You cannot choose to sneak attack non-lethally.
Murderous Presence
Also from 3rd level you gain proficiency in the Intimidation skill. If you already had this, you instead gain a proficiency in a skill of your choice from the rogue list.
Bloodlust
From 9th level as an action you can choose a target you can see within 60ft and fill them with an immense bloodrage, urging them to murder on your Lord Bhaal's behalf. They must succeed on a wisdom saving throw (DC=8 + your proficiency bonus + your Constitution modifier) or be affected by Rage (as a 1st level barbarian). You then designate another creature within range you can see. The enraged target must do everything they can to kill the designated creature, as fast and as brutally as possible.
Bloodlust lasts for 1 minute. The affected creature can make a new saving throw at the end of each of their turns to end the effect, but it otherwise does not end until either the targetted or the designated creature is dead.
A creature can willingly fail their saving throws against Bloodlust. This feature can be used once, refreshing on a short or long rest.
Advanced Death Attack
Also from 9th level if you use your bonus action on either Cunning Action or Steady Aim, you can also choose to use your Death Attack feature as part of the same bonus action (assuming you have a use available).
Domain of Bhaal
From 13th level you gain access to a measure of spellcasting ability. You can cast each of the following spells once per long rest, without providing material components: False Life, Ray of Sickness, Blindness/Deafness, Ray of Enfeeblement, Animate Dead and Vampiric Touch.
Vampiric Touch's spell attack counts as a finesse weapon for the purposes of sneak attack when cast from this feature, though only the spell's damage and not your sneak attack are included for health restoration purposes.
Constitution is your ability modifier for these spells attack rolls and save DCs.
At 19th level you also gain the ability to cast Blight and Death Ward, again once each per long rest.
Mastered Death Attack
From 18th level, a failed save against your Death Attack now Paralyzes the target instead of Incapacitating it, and it lasts until the end of your next turn. If a target is immune to Paralysis, but not Incapacitated, they are instead still Incapacitated.
Last Breath of Bhaal
From 18th level the magic of the Lord of Murder's last gasp allows you to return yourself from the dead. If you are killed, your body is affected by the True Resurrection spell after 1 hour, assuming you have not already been resurrected. During the time you are dead, your body shows no signs of life or magic affecting your corpse.
Last Breath of Bhaal can be used once, refreshing after 1 week. If you kill another creature whose CR is at least 1, it immediately becomes available for use again.