Are there any mechanics for becoming a warlock patron?

Question

So our home campaign is, as all really good campaigns are, a hideous conglomeration. Chunks of other campaigns, including several published ones, have been combined, and a whole lot of homebrewing has been tossed in, especially bits about warlocks and their patrons. This culminated in our gnome warlock, who had made his pact with the Queen of Air and Darkness, manipulating his way into a position as an archfey just so he could break the pact and make one with himself.
This is, obviously, not covered by the rules normally, and I have no questions about that.

What I do have a question about is whether there are any rules out there covering being a patron for somebody else.

I'm specifically looking for information that would cover.

• how many warlocks you can be a patron for.

• whether there is a cost for the patron.

• is that little gnome going to have to sacrifice levels or spell slots to give someone else magic power.

  • is he simply serving as a conduit for power from the Feywild itself?

  • anything mechanically involved.

  I'm trying to work out how our tiny archfey could build a coterie of warlocks, in a similar fashion to wizards taking on apprentices or a knight hiring on squires.

For reference, I've checked through the following books: the PHB, DMG, CoS, Dragon Queen, Rise of Tiamat, Storm King's Thunder, Xanathar's Guide, Mordenkainen's, and Volo's. If there's a sourcebook that addresses warlock-patron relationships from the patron's end, that'd be preferred, and I'm cool with third-party work. Barring that, homebrew is okay, but my goal is to find mechanics that are internally consistent, so it needs to jibe with what the PHB has to say on patrons.

Answer 1

A warlock can become a patron, but there are no specific rules for it

According to Dungeon Master's Guide p.38, becoming a patron is indeed a possibility for a warlock who reaches 20th level:

Characters who reach 20th level have attained the pinnacle of mortal achievement. Their deeds are recorded in the annals of history and recounted by bards for centuries. Their ultimate destinies come to pass. A cleric might be taken up into the heavens to serve as a god's right hand. A warlock could become a patron to other warlocks.

However, warlock patronage isn't bounded by any particular game rule. Unlike the deity rules originating in older editions of D&D, there's no ranking system to show the relative power of different patrons, nor any rules for how many followers they should have.

How many warlocks per patron?

This number is arbitrary and highly variable and not bounded by any game mechanic. As per Player's Handbook, p. 108, Otherworldly Patrons:

Some patrons collect warlocks, doling out mystic knowledge relatively freely or boasting of their ability to bind mortals to their will. Other patrons bestow their power only grudgingly, and might make a pact with only one warlock.

What does it cost the patron, and what is their power source?

There's no evidence that it costs the patron anything, nor any rule to suggest the source of the being's power. We do know that patrons are exceptionally powerful beings in their own right:

The beings that serve as patrons for warlocks are mighty inhabitants of other planes of existence—not gods, but almost godlike in their power.

Archfey have a limited amount of lore, but archdevils and demon princes traditionally occupy entire layers of the Nine Hells or the Abyss because they are powerful, rather than drawing power from those planes. Certainly, however, legendary creatures often gain additional combat abilities while in their lair.

There's no text which would suggest a patron gives up part of their strength to create a warlock. In the 3rd edition sourcebook Complete Arcane, the warlock was described as giving up part of their soul to their patron in payment, which if anything ought to make the patron more powerful.

Nevertheless, a weaker patron having limits is wholly within the realm of possibility. Dungeon Master's Guide p.38 suggests that a normal character should be at least 20th level to become a patron, but this would still place you as one of the weakest. Patrons are described as "nearly godlike" in their power, with Tiamat (CR 30) setting the upper bound for "nearly" godlike. Examples of patrons with available statblocks include Baphomet (CR 23), Fraz-Urb'luu (CR 23), Orcus (CR 26) Demogorgon (CR 26) (source: Out of the Abyss).

Answer 2

No, there are no mechanics provided for a player character to become an "otherworldly patron"

The "Otherworldly Patrons" section of the warlock class description states:

The beings that serve as patrons for warlocks are mighty inhabitants of other planes of existence—not gods, but almost godlike in their power. Various patrons give their warlocks access to different powers and invocations, and expect significant favors in return.

Some patrons collect warlocks, doling out mystic knowledge relatively freely or boasting of their ability to bind mortals to their will. Other patrons bestow their power only grudgingly, and might make a pact with only one warlock. Warlocks who serve the same patron might view each other as allies, siblings, or rivals.

Earlier parts of the warlock class description reveal other details about typical kinds of patrons, and the warlock's relationship with their patron:

A warlock is defined by a pact with an otherworldly being. Sometimes the relationship between warlock and patron is like that of a cleric and a deity, though the beings that serve as patrons for warlocks are not gods. A warlock might lead a cult dedicated to a demon prince, an archdevil, or an utterly alien entity—beings not typically served by clerics. More often, though, the arrangement is similar to that between a master and an apprentice. The warlock learns and grows in power, at the cost of occasional services performed on the patron’s behalf.

[...]

Stories of warlocks binding themselves to fiends are widely known. But many warlocks serve patrons that are not fiendish. Sometimes a traveler in the wilds comes to a strangely beautiful tower, meets its fey lord or lady, and stumbles into a pact without being fully aware of it. And sometimes, while poring over tomes of forbidden lore, a brilliant but crazed student’s mind is opened to realities beyond the material world and to the alien beings that dwell in the outer void.

[...]

As you make your warlock character, spend some time thinking about your patron and the obligations that your pact imposes upon you. What led you to make the pact, and how did you make contact with your patron? Were you seduced into summoning a devil, or did you seek out the ritual that would allow you to make contact with an alien elder god? Did you search for your patron, or did your patron find and choose you? Do you chafe under the obligations of your pact or serve joyfully in anticipation of the rewards promised to you?

Work with your DM to determine how big a part your pact will play in your character’s adventuring career. Your patron’s demands might drive you into adventures, or they might consist entirely of small favors you can do between adventures.

What kind of relationship do you have with your patron? Is it friendly, antagonistic, uneasy, or romantic? How important does your patron consider you to be? What part do you play in your patron’s plans? Do you know other servants of your patron?

As you can see from these excerpts, a warlock is a warlock by the very nature of their power and its connection to their patron. They get a portion of their patron's power in exchange for something, though the exact details of that relationship are left for the player to work out with their DM.

Ultimately, though, once they're at the point at which they're equal in power to their patron... Well, there's no more knowledge to learn; no greater power to gain. (And it makes no sense to make a pact with yourself to get a portion of your own power and knowledge.)

You might theoretically become powerful enough that others will want to make pacts with you to gain a portion of your own power or knowledge - but that's generally the conclusion of your story arc as a playable character, and/or the start of that character's arc as an NPC in some sort of sequel adventure that's set in the future of the previous campaign in which you played that character.

Once you're virtually a god, there's not really much higher to go as a PC - certainly nowhere that D&D 5e is designed to handle as a system. It can make for a cool story beat, but that's about it.

Even from the DM perspective of running a patron "NPC", no such detailed mechanics are provided about the patron-warlock relationship. Besides the broad guidelines I've referenced above, it's basically up to the DM to determine such details - no particular mechanics are described in any official 5e materials. In short, the rules leave it to the DM to work out with their player.

Answer 3

As far as I know there aren't any

This might not be what you're looking for but when I ended my last campaign with everyone at twentieth level and all having achieved conceivable goals the warlock that became an archfey used same rules generally used for Avatars here's this and I counted them as a Lesser Deity for how to decide the number they got.

This was only for story purposes and how the world was affected.