I have considered this extensively but I am interested in hearing feedback.
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Careful Spell Metamagic Feat
Prerequisite: able to cast 1st level spells.
When you cast a spell that forces other creatures to make a saving throw, you can protect some of those creatures from the spell's full force. To do so, you expend 1 spell slot, and choose a number of those creatures up to your Charisma ,Intelligence, or Wisdom (chosen when you gain this feat) modifier (minimum of one creature). A chosen creature automatically succeeds on its saving throw against the spell.
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The above represents a series of feats that the DM would be able to incorporate to the game to add more verity to spell casters in general with out overshadowing the Sorcerer class. Other meta magic feats could cost 2 spell slots (or a level 2 spell slot.) as applicable.
I don't think there are any AoE spells with saving throws that doesn't deal damage and doesn't let you choose your targets?
Just use your first idea for those spells. Or you could give them advantage or +5 to their roll instead.
EDIT: Nvm, just remembered that there are.
EDIT2: Also, what level does the expended spell slot have to be at? Any bonuses for using a higher level spell slot? Any thoughts of changing it to "once per short rest" or "increase casting time by 1 (or more) actions" instead?
I have considered this extensively but I am interested in hearing feedback.
________________
Careful Spell Metamagic Feat
Prerequisite: able to cast 1st level spells.
When you cast a spell that forces other creatures to make a saving throw, you can protect some of those creatures from the spell's full force. To do so, you expend 1 spell slot, and choose a number of those creatures up to your Charisma ,Intelligence, or Wisdom (chosen when you gain this feat) modifier (minimum of one creature). A chosen creature automatically succeeds on its saving throw against the spell.
_______________________
The above represents a series of feats that the DM would be able to incorporate to the game to add more verity to spell casters in general with out overshadowing the Sorcerer class. Other meta magic feats could cost 2 spell slots (or a level 2 spell slot.) as applicable.
Instead of automatically succeeding, how about using the same effect as Sculpt Spells from the wizard's School of Evocation?
Half damage on failed save, and no damage on success.
A good suggestion, but what about spells that do not deal damage?
I don't think there are any AoE spells with saving throws that doesn't deal damage and doesn't let you choose your targets?Just use your first idea for those spells. Or you could give them advantage or +5 to their roll instead.
EDIT: Nvm, just remembered that there are.
EDIT2: Also, what level does the expended spell slot have to be at? Any bonuses for using a higher level spell slot? Any thoughts of changing it to "once per short rest" or "increase casting time by 1 (or more) actions" instead?
The expended spell slot would be level 1 at a minimum. A level 2 spell slot would count as two level 1 spell slots for these purposes.
I did consider having the ability be once per short rest, but that felt a little restrictive to me, good idea though!