The X

You have made a pact with the mysterious and ancient X, beings that consume the shapes, abilities, and memories of past hosts. Whether or not you know how this being came to reside in you, it provides you access to the memories of older hosts and changes you to be able to survive better. The motives of the X are unknown, but it is clear to those who deal with them that they enjoy collecting new abilities and memories.

*This Subclass is inspired by Nintendo's Metroid franchise. I do not have access to the Xanathar's so the spells Insect Plague and Zephyr Strike are not available in the character builder.

X Extended Spells

The X 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.

X Expanded Spells
1st - entangle, zephyr strike
3rd - alter self, enhance ability
5th - animate dead, meld into stone
7th - polymorph, black tentacles
9th - insect plague, modify memory

Memories of Old

Starting at 1st level, your patron can some of it's stolen memory or ability for a time. Whenever you finish a short or long rest, choose one skill or weapon to become proficient with until you use this feature again.

Combat Form

Additionally at 1st level, your patron gives you the ability to shape your body for combat. As a bonus action, you can modify your physicality to better fight up close. This change lasts for 1 minute, unless you use this feature again or drop to 0 hit points.

You choose the shape each time you use this feature: 

Voltaic Armor: Your skin crackles with electricity, creating a deadly barrier around you. Whenever you take damage from a creature within 5ft of you, you can use your reaction to deal 1d6 lightning damage to that creature.

Powerful Build: Your muscles swell unnaturally, giving your attacks more strength than normal. Once per turn, when you deal damage from a melee hit, you may add your proficiency bonus to the damage you deal.

Protective Hide: Your skin hardens, becoming a shell to protect your body. If you are not wearing armor, your AC becomes 13 + your dexterity bonus.

You can use this feature a number of times equal to your proficiency bonus. You regain all expended uses after you finish a long rest.

Amalgamate

Starting at 6th level, whenever you kill a creature within 60 feet of you, you can absorb some of its abilities or memory. You gain one proficiency that the creature had, until after you finish a long rest. If the creature had access to spells, you can instead gain the ability to cast one of the spells it had. This spell must be of a level that you can cast, and the ability to cast it goes away after you finish a long rest.

Fury of the Fallen

Starting at 10th level, your patron begins to have more interest in your survival. To better protect you, your patron bolters you when you become weak. Whenever your hit points drop to one fourth of your max hp (rounded down), you gain 2d8+ your Constitution modifier temporary hit points. In addition, your combat form also improves:

Powerful Build: Your patron also expands your ability to use magic, giving your spells an even greater edge. Once per turn, you may add your charisma modifier to the damage of a spell you cast.

Protective Hide: Your patron strengthens your hide, protecting it against certain attacks. Choose one damage type. You gain resistance to that damage type.

Voltaic Armor: Your patron improves your armor, making it stronger. Your Voltaic armor deals an additional damage die of lightning damage.

Gift of the Persistent

Starting at 14th level, you have gained your patron's respect, allowing you to persist for a while after death to find a new form. When you are reduced to 0 hit points but not killed outright, you turn into the floating gelatinous form of your patron. While in this form, you receive 3d8 + your Constitution Modifier hit points and a flying speed equal to your land speed. As an action choose one creature within 5 feet of you with less than half of its hit points. That creature must make a constitution save equal to (8 + your proficiency bonus + your Charisma modifier) or be absorbed into your patron. Your patron then uses the creature's body to remake your own, and you return to life with health equal to one fourth (rounded up) of your max hit points. This form lasts for 1 minute. If you do not create a new form from another creature in that time, you die.

Once you use this feature you cannot do so until you finish 1d4 long rests.