The Marilith

With a Marilith as your patron, your dreams are full of military instruction and battles. They hurt. The Marilith is a demon, and it is not your friend. Once you prove yourself in a one on one battle that lasts for seemingly an eternity, your next stage of instruction can begin. Once you complete a second battle in the Abyss, you are ready for transformation. 

 

But the education goes both ways. Some Mariliths are itching for knowledge that does not contain swords and armor. Some with to know about Material Plane etiquette, or knowledge of dialects or spells unrelated to combat. For this reason, some Mariliths travel to Gehenna or Hades to capture an Arcanaloth and keep it hostage for knowledge. But with a Warlock as a partner, it is much easier. 

Expanded Spell List

The Marilith lets you choose from an expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you.

Fiend Expanded Spells

Spell Level	Spells
1st	compelled duel, ray of sickness
2nd	barkskin, shadow blade
3rd	crusaders mantle, haste
4th	elemental bane, stoneskin
5th	dominate person, steel wind strike

Snake's Stratagem

Starting at 1st level, the Marilith gifts you a part of its battle prowess to aid you. You gain proficiency in medium armor and scimitars. You also gain resistance to Poison damage, and you gain advantage on saves made to thrown off he poisoned effect. 

Additionally, you can use the Parry reaction once per round. 

Also, you learn to speak, read, and write Abyssal if you don't already know it.

Marshal The Troops

Starting at 6th level, the martial power of the Marilith can aid you in times of need. You can use the Commander's Strike or Rally battle maneuvers from the Battle Master page. Your superiority die is a d6 at level 6, a d8 at level 10, and a d10 at level 14. 

 

You can use each maneuver once per long rest. 

Serpent Savant

Starting at 10th level, your body begins to transform from the constant influence of your serpentine Patron. You gain +1 bonus to AC as a thin sheen of scales cover your body, and you gain 15 feet of truesight as your eyes become bright yellow and gain slits for pupils. You can also smell if food or drink is poisoned with no Medicine check.

Fiendish Commandant

Starting at 14th level, your demonic transformation is complete. While you are not a Marilith, you are as close as you will get. When you reach this level, the night is ruined by the painful growth of two arms, granting you the total of four unless you are missing any. As long as you have these arms, you can hold a scimitar (or simple melee weapon) in each hand, and take four attacks when you take the Attack action. If you take more than two attacks, you forgo any bonus actions or reactions you could take. 

In addition, you can teleport up to 30 feet as a bonus action an amount of times equal to half your charisma modifier, rounded up. You regain these uses when you finish a long rest.