League Assassin

The League of Assassins is perhaps the most well known Assassin's Guild in the world, and it is certainly the most feared. It accepts only a few candidates each year, and fewer still survive the recruitment process. Their recruits come from all different races and walks of life, but they all share two things: They know that the world is corrupt, and they seek to purge it of that corruption, one death at a time.

When you chose this subclass at 3rd level, think about what made your character so special, to not only be selected as a recruit of the League but to pass their gruelling initiation process. Additionally, think of why you left the League headquarters on the island of Nanda Parbat. Were you sent out on an assignment, to bring death to one of the League's enemies? Were you one of the few who managed to split from the League on good terms, or were you one of even fewer who managed to escape from the island. And if you did leave the League, what caused you to make that decision?

The League is an ancient organization, with many traditions and secrets, the oldest of which being the Prophecy: He who survives the blade of Ra's al Ghul shall become Ra's al Ghul.

 

Assassinate

Starting 3rd level, your League training has made you deadliest when you get the drop on your opponents. You have advantage on attack rolls against any creature who hasn't taken a turn in combat yet. Additionally, any hit you score against a creature that is surprised is a critical hit.

League's Respect

Additionally, the League has safehouses in just about every city in the world. Chose up to three cities with which you are familiar (places you've lived in or stayed for more than a year; in this case "city" includes any settlement with over 5,000 citizens). You know the location of all League safehouses in those cities (as a general rule, there's 1 safehouse per 5,000-10,000 citizens). A safehouse is protected by magic so that only a League member (and those they invite in) may enter. Each safehouse functions as a mordenkainen's magnificent mansion (with the previously mentioned alteration), and contains all manner of mundane weapons and tools, as well as magic items (generally only common or uncommon, as up to your DM). You may learn the location(s) of additional safehouses as you increase in levels if you spend extended periods of time in a specific city (again, up to your DM).

Master of Pain

The League of Assassins are masters of torture, and are said to be able to inflict and relieve pain with the slightest touch. Starting 9th level, you can cast cure wounds and inflict wounds at their lowest level a number of times equal to your Charisma modifier (minimum 1), and regain the ability to do so after completing a long rest. For example, if you had a Charisma score of 16 (a +3 modifier), you would be able to cast both spells three times each per long rest. Charisma is your spellcasting ability modifier for these spells.

By 17th level, you gain greater control over the forces of life and death. You gain the ability to cast both heal (with a range of touch) and harm once each, and regain the ability to do so after completing a long rest. 

Blade Mastery

Members of the League of Assassins are famed for their skill with the blade. At 13th level, you gain the following abilities:

Weapon of Choice: Chose a weapon with the finesse property you're proficient with (daggers, rapiers, scimitars, or shortswords). You score critical hits with that type of weapon on a 19-20, and attacks with that type of weapon count as magical for the purposes of overcoming resistance and immunity.

Parry: When a creature hits you with a melee weapon attack, you can use your reaction to add your proficiency bonus to your AC for that attack. If this causes the attack to miss, and you're wielding your Weapon of Choice, you can use your Riposte feature as part of that same reaction.

Riposte: When a creature misses you with a melee weapon attack, you can make a melee attack against it with the finesse weapon you're holding. If that weapon is your Weapon of Choice, you can add your Charisma modifier to the damage dealt.

Death Strike

Starting 17th level, you become a master of instant death. When you score a critical hit against a creature, it must make a Constitution saving throw (DC = 8 + your Dexterity modifier + your proficiency bonus). On a failed save, double the damage of your attack against that creature.