I admit this is a matter of personal taste, but I HATE the very concept of limited spells known. Detest it, and detest classes that are built that way. Every class has a big, beautiful spell list (some more than others, but that's neither here nor there), and a player of a limited-spells-known class will never get to use most of them. It's a waste. It also limits my (as a DM) flexibility, because I can't count on the characters having access to any particular magic when I make my adventures.
So.
I have made house rules that allow for some flexibility in the classes that don't have it per the PHB. Bards have a "song book" that mostly works like a Wizard spellbook (except it's written in a idiosyncratic musical notation, get it?), and they prepare spells with daily music practice. Warlocks can "borrow" 2-3 spells (in addition to their regular Spells Known) from their patron at the end of a long rest, and can cast them using a regular spell slot or Mystic Arcanum slot.
But what about Sorcerers? I'm struggling to think of a house rule that would allow for some flexibility while being consistent with the classes' concept of a natural, intuitive spellcaster. Any ideas? Has anyone implemented a similar rule?
(Please no replies of "Don't do this" or "That isn't what the Sorcerer is". I don't care. I'd rather just nix the class entirely than have a class with limited spells known. Solutions only, please. Thanks.)
I'll preface by saying I have a different philosophy on sorcerers. That said...
They're intuitive, right? Making this up as they go along without any theory or study? So how about they can replicate any spell if they've seen it or heard about it, but there's a risk? I'm envisioning something like a % chance of "unfortunate or potentially dangerous consequence" borrowing the familiarity table of the
teleport spell.
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Familiarity
"Permanent circle" or "associated object" would be knowing the spell or having a scroll of it. Cast as normal.
"Very familiar" would be sorcerer spells that match the PC's overall theme/sub-class or spells cast regularly by fellow PCs.
"Seen casually" would be spells cast by NPCs in town or recurring spellcasting monsters.
"Viewed once" would be a spell the sorcerer just witnessed being cast.
"Description" would be a spell the sorcerer heard described by another NPC or in a book.
"False spell" would be the player trying to make something up on the spot, knowing full well their PC doesn't know anything about the spell, or other corner case scenarios. Could include spells not on the sorcerer spell list too, depending on how much access to other spell lists you want to give sorcerers.
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So you'd have "mishap" as in the spell backfires or the DM makes up something suitably nasty. Think of this as the DM answering "no, and..."
"Similar spell" would mean the sorcerer accidentally casts a similarly leveled spell from the same school instead. Think of this as the DM answering "no, but..."
"Off effect" would mean the sorcerer casts the right spell but there's a twist or complication to its effect. For example, a
lightning bolt emitting a crack of thunder alerting all monsters within a mile. Think of this as the DM answering "yes, but..."
"On effect" would mean the sorcerer casts the right spell as desired.