Instead it is "the origin of power is open to player's interpretation".
Or, just as importantly, the DM's. Things don't fly at a table unless a DM gives a go-ahead.
And the server rules state that warlocks become warlocks through specific pacts; that you CAN play other pacts (or not have one!), but it won't have official DM team approval.
You'll need to negotiate the pact prior to level 1, meaning your character's social/diplomacy skills are zero.
You defeat the first sentence with the second sentence. How could a wizard go through wizarding school if he didn't ever have magical abilities? He wouldn't be able to cast a cantrip, and he wouldn't have the Knowledge: Arcana skill and such to graduate from his classes! Well, clearly, he must have been able to learn it, because after years of dedication
he did.
Sometimes, stuff falls into a backstory situation. Or sometimes stuff just exists outside of the simulation that is the game itself, and has to be explained by other means. Sometimes you have Commoners or Adepts becoming character classes and trading out their NPC levels for PC levels. Sometimes you have DM fiat.
Whatever the case, the argument of "well before level 1 you don't have skills so NYEH" is silly.
Meaning if a warlock is young then he or she somehow successfully negotiated a pact at the age of 12 or 14. I can't find a table, but IIRC the "prior to young adult age" had mental stat penalties.
You know? I think that's actually very believable. Teens have plenty of intellect; they just don't have the actual education or self-awareness to make good decisions, typically speaking. That is, a teenager is just as capable of absorbing new information and understanding difficult concepts, but they don't necessarily have the experience or traits necessary - the traits summarized by the D&D statistic "Wisdom" - as well as an adult can.
Ergo, a fourteen year old might very well be able to negotiate a pact, and because they think they're the smartest cookie around won't realize how goddamned stupid it is for them to try and do that. In fact, I think that's going to be my next character: someone that made a TERRIBLE choice as a kid. Yeah. This works.
I can't find a table, but IIRC the "prior to young adult age" had mental stat penalties.
The only thing I remember for young characters is in Pathfinder -
click. Older characters are covered
here, under aging effects.
Which would simply indicate latent abilities awakening. Same thing as picking a sorcerer level late (the dragon blood thing). This is in line with "warlocks are born, not made".
...unless you wanted to roleplay accepting a pact. Which you could.
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I think what's noteworthy here is that while you are this singular line, everything should lead back to the original topic: are we going to add new powers or not? Your original argument was "No, because that's lore-breaking," but if the powers come from sources like demons, devils, the fey, etc., then it doesn't seem terribly amiss for shapeshifting powers to be provided.
And the DM team does say those pacts are the pacts that exist: celestial, demon, devil, fey, slaadi. Am I missing any? And because those forms exist, and because shapechanging stuff for warlocks IS in the game, the suggestion is just to provide more shapechanging options in a medium where this is already accepted and in lore where, yes, warlocks get their power from the patrons I just listed.
Given that, it seems ENTIRELY sensible to allow new shapechanging options. If they exist, why would a warlock whose powers come from the Fey - whether simply unlocked or actually GIVEN by the Fey via a pact - turn into a goddamned Hellhound? Why not a Fey creature? "Give more options" is the answer, because you bet your butt those shapeshifting powers aren't gonna be removed any time soon.
And while I understand that you like the concept of the warlock whose magic stems from a source independent of Pacts, I will quote the DM team one last time...
The DMs have discussed warlock pacts, and below are the pacts the DMs support. Other pacts are not disallowed, but won't be supported by DMs. If you wish your warlock biography to be approved by the DMs, you will have to be pacted to one of the pact givers from below.
So, can you do it? Yes. But that's not the server lore. The server lore says that if you're a warlock, you MUST be Pacted with the Celestials, Demons, Devils, Fey, or Slaadi to get your warlock powers. You made a pact - yes, perhaps before level 1, or before actual play, or before your character had PC class levels - or inherited one. That's just how it is.
You're not disallowed from doing it your way, but you can't tell other people they're doing it wrong because this is the Lore on BGTSCC.