using this variant rule, when a sorcerer learns a new spell of first level or higher at 6th or 10th level, they can choose to learn a spell from any spell list, including this one. If the spell they choose is from the sorcerer spell list, it is treated as normal, but if it is not, a few more rules apply to it:

-it is still treated as an normal sorcerer spell for you, charisma is your spellcasting abillity for it, you must expend spell slots as normal to cast it 

-you cannot choose a spell of a level you cannot cast to be learned this way.

-there is an maximum number of times you can use an spell learned in this manner between long rests equal to twice your charisma modifier

-immedeatly after the spell ends you must make an constitution saving throw or take 1d4 force damage, DC equals 10 + the spells level

basically, this variant rule adds s little bit of mystique to the sorcerer, making them feel a bit more unpredictable, not every sorcerer will manifest their powers in exactly the same way and it makes sense for some sorcerers, particularly wild magic sorcerers, to occasionally have truly rare abillities, no idea of this could ever work or if it would make the bard feel less special or if it even is a bit underpowered due to the massive constraints put on these rare "special" spells. Could add a little bit of storytelling potential by connecting this new spell ether to an event in the campaign or as part of backstory, how an sorcerer might have been ether magically designed or selectively bred to fulfill some kind of purpose like raising the dead or producing water or serving as an living hell portal, sky is the limit on how far you want to take this

If you’re going to limit it, double cha might be too much being most sorcerers would have at LEAST +3 Charisma and 6 8 or 10 might be too much if you want to put a limit
not sure if I really understand the last part when there’s also a limitation on it already

Quote from Bamb00z1ed >>

If you’re going to limit it, double cha might be too much being most sorcerers would have at LEAST +3 Charisma and 6 8 or 10 might be too much if you want to put a limit
not sure if I really understand the last part when there’s also a limitation on it already

 mostly just a flavour thing i guess, for these rare, incredebly special spells it might be more physically draining than the typical sorcerer spell, also the limitation is meant to not be too limiting, whilst still preventing an player to spend all their spell slots on some absurd metamagic combo

Just make it a spell that's of a level you can cast, that's literally all you need to do for restrictions.

Basically the Bard's Magical Secrets?

I could see a minor variant for certain subclasses, not as a main feature. I prefer the Origin Spells they've started doing (as for Aberrant Mind and Clockwork origins). 

I agree that Origin spells are better, but I was evaluating this option on its own.

Quote from Cyb3rM1nd >>

Basically the Bard's Magical Secrets?

I could see a minor variant for certain subclasses, not as a main feature. I prefer the Origin Spells they've started doing (as for Aberrant Mind and Clockwork origins). 

 similar to the bards magical secrets, but available to any sorcerer that allows for more flavouring and reflavoring as nessesary while being kinda dangerous becuase of unexpected metamagic