Hello everyone! My friend and I were working on some side projects on the side and we came up with a cool patron idea for the Warlocks. It revolves around your patron either living or being housed inside of you instead of being completely removed or not connecting with you. This subclass is a bit of an RP starter as well as a buff to a warlock's spells and survivability on the battlefield. As always, anyone is free to use this for a playtest (just give credit where it is due), and I am eager to hear feedback and comments on this idea

This doc will also include three Invocations that I made to compliment this subclass and be more in line with the other patron options.

//***Symbiosis Patron***\\

"One would think the provider of immense power wouldn't be a measly parasite looking for a safe haven, but desperate patrons tend to have something to lose and will even stoop low enough to graft themselves onto lowly hosts when necessary. Patrons of the Symbiosis pact often house either a piece of their body or soul into another living being and give immense powers for the chance to continue living on through their host. While a patron may have malicious intent and may come to hate their current host, they have no choice but to keep them safe because if one symbiotic creature dies, so does the other."

Expanded Spell List: Your Symbiosis Patron 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.

Symbiotic Ascension: Starting at 1st level when you choose this patron, your Hit Point maximum increases by 1 and increases by 1 again whenever you gain a level in this class.

Symbiote's Influence: At 1st level, you learn the Thorn Whip cantrip. This cantrip does not count against your number of cantrips known.
Additionally, you have advantage on concentration checks with your warlock spells. *(This feature was suggested by user waitwhatplease)

Parasitic Siphon: Beginning at 6th level, whenever you cast a spell using a warlock spell slot, you regain Hit Points equal to your Charisma modifier (minimum of 1).

Uncanny Deflection: Starting at 10th level, when an attacker that you can see hits you with an attack, you can use your reaction to toughen your body and halve the attack's damage against you for that attack.

Parasitic Grasp: At 14th level, you gain the ability to extend your patron onto another humanoid's body and siphon their life force. You can use an action to make a melee spell attack against a humanoid creature. On a hit, the target takes 3d10 necrotic damage and it is considered grappled by you. You can use your spell-casting modifier instead of your Athletics while maintaining this grapple. As long as you are maintaining the grapple, you can use your bonus action on subsequent turns to cause 3d10 necrotic damage to the grappled target.
If the grappled target succeeds on it's check to escape your grapple, they take 4d6 slashing damage.
Once you use this feature, you can't use it again until you finish a long rest.

Invocation List:

Symbiotic Decay:

• Prerequisite: The Symbiosis patron, Eldritch Blast cantrip
• Whenever you cast Eldritch Blast, you can choose to change the damage type of one or multiple beams to deal Necrotic damage instead of Force damage.

Parasitic Familiar:

• Prerequisite: 5th level, The Symbiosis patron, Pact of the Chain feature
• When you choose the form for your Pact of the Chain feature, you can have your Symbiosis patron take over a creature that is CR 1/8 or lower as a familiar form. The controlled creature gains the benefits of being your familiar, it's Intelligence, Wisdom, and Charisma scores increase to 10, and it can speak one language that your patron knows, but must abide by all other rules set in place by your Pact of the Chain feature and it cannot be a Construct, Ooze, or Undead creature.

Symbiotic Mending:

• Prerequisites: The Symbiosis patron
• When you roll a hit die to regain Hit Points, the minimum number of Hit Points you regain from the roll equals your Charisma modifier (minimum of 1).

I like the idea of this durable warlock. Its a little bit body horror which I like. 

I will say that it feels like there is opportunity to give it Thorn Whip as bonus cantrip like The Celestial and the Undying Patrons do. But that may make it a bit to on the nose interms of the Venom Symbiote imagery.

Sooo nasty...right up there with the spore Druid. I like it!

Hm... That's actually a good idea. I've been pondering what else I should add to the Co-dependent Casting feature and that is just the sort of thing that's needed! Will have to change the name of the feature though, any ideas?

Thank you! Glad you enjoy it!

I personally love this idea and almost wish this was an official option, because quite frankly, I find this to be a great start for some interesting backstories. Whenever I made a sort of symbiotic or parasitic entity I always resorted to the sorcerer, but this really poses some interesting ideas.

Thank you. And yea that's why my friend and I designed it, so that there would be more options for a DM to role-play a patron on a more personal and different level than normal. But by all means, feel free to make a character using this subclass and tell me how it goes!

One thought...it kind of looks like Uncanny Deflection gives you resistance to all damage once per round. Just wondering if that is balanced. Fiend and Hexblade have similar features at 10th level...Both of those features seem a little bit more limited. Fiend is a single type of damage and Hexblade is just a cursed target. Just my two cents. This is a very thoughtful Patron by the way. . . 

I think Uncanny Deflection is balanced verses the Hexblades Armour of Hexes Which can cause an attack to completely miss, and the Fiends Fiendish Resistance provides constant protection against damage of a single type without using up a reaction.

Uncanny Deflection is a reskin of the Rogue's Uncanny Dodge feature. Note it is resistance to ONE attack, not an entire round so I feel it's more balanced out.

Sorry I missed the “reaction” part. My bad.

I was actually thinking about it this morning! Damn, thank you for making it! Hope at least i'd see a more official version of it but i am willing to try this one out in my next one shot.

We can only hope WotC decides to give me a shot XD. And good, playtest it and tell me how it went

The one shot went very well. I took a Goliath for this class gaining me a lot of tankiness, though i gotta say uncanny deflection is very powerful even for a reaction. The grappling thing was very fun since i took a Goliath with proff in athletics it made it way easier to grapple and pin down but it felt too powerful for 3d10 each turn, with Bestow Curse. I was dealing a crazy amount of damage just in one turn. 

also having the grapple not stopped if you do anything else made it ridiculously strong. Maybe have the warlock unable to do anything else otherwise the grapple is broken is way more balanced imo. 

Thanks for getting back to me! Glad it worked out well!

Uncanny Deflection is just reskinned Uncanny Dodge from the Rogue class so I feel that is fine there. Now as far as the grapple goes, if I read the rules correctly, you don't need to use your action or anything to maintain a grapple. You can still perform other actions (as long as you have one free hand and one grappling the creature) while holding onto a creature so that's fine there. The damage is the most concerning thing, not sure if I should lower it or not (maybe make it 3d8 instead). Trick is, if the grapple is broken, the ability is on cool down for a long rest and you have to use a bonus action to inflict the damage anyway.

I'll talk it over with my friends and see what they think but thank you for the input! Also, if the damage has to be nerfed, should I keep the fact that if an enemy succeeds on breaking free they take damage?

I like this patron. Really cool idea. 

1) WHy can't they select a ooze-like creature for Parasitic Familiar?

2) Why do they take damage for escaping the grapple? You can also rephrase it as, "To escape the grapple, the target must make a Strength (Athletics) check versus your Spell save DC." OR "To escape the grapple, the target must make a Strength (Athletics) check versus your Charisma (Athletics) check."

3) Proficiency in Intimidation or Deception might be appropriate for this patron.

4) Parasitic Siphon, do any other spellcasting classes have a similar ability where they regain hit points after casting a spell using that classes spell slots?

Thanks for the input! Hope I can answer your questions well enough and you can see my reasonings

1. In my eyes, oozes tend to be less living creatures and more just sentient goop. It's hard for a parasite to latch onto something when just touching it is harmful or deadly to you so that's why I left it out

2. Escaping a grapple is always based on the grappler's Strength(Athletics) check verses the target's Strength(Athletics) or Dexterity(Acrobatics) check so that's why I left the ruling out (and added the fact you could use your spell-casting modifier instead of your Athletics score for those who tend to be on the weaker side for this ability). Additionally, the idea is that the Symbiote patron latches onto the target in a parasite like fashion and the act of ripping yourself out of it is so violent it causes damage (and also helps make the ability feel a bit more potent if the target is really strong and gets out of your grapple first try). Is there a need to change it?

3. As a warlock, you can get those as starting skill's from the class and you can get Deception from some Warlock Invocations so I don't see them as really necessary

4. I believe the Life Domain Cleric has a similar ability (Its when you heal a target with a cleric spell slot, you regain Hit Points as well)

No real comment other than this is amazing and I wish I had the ear of the dev's to help make this a reality. 

I really like this

How do i make my character with this, id really like to!