So I have a player with a shadow sorcerer in my current campaign and she has picked spells that deal cold and necrotic damage over some of the higher damaging fire/lightning spells in order to fit the flavor of her backstory/origin.
I know she wants to be a Blaster character and 5th level is coming up quicker than anticipated and I know fireball is on its way. I was thinking of giving her a modified fireball that deals necrotic (or cold) damage INSTEAD of fire to better match the theme. I know Tasha's gave a new metamagic that lets sorcs change the damage type of spells, but I don't want her to have to spend a SP every time just to fit theme.
I don't imagine switching fire damage for necrotic (or cold) would cause to many issues, both of them are on par with fire in terms of monster resistances so I don't think I've made the spell "better" just different. But I also know I could be overlooking something.
In terms of balance, the thing to watch with changing the damage type is how common the resistance is. I'm not totally sure, but I think resistance to necrotic damage is rarer than resistance to fire damage. That's why many people thing thunder damage is superior - resistance is rare. So there's a small shift in the player's favor there. But you just need to make sure that they are running into things with necrotic damage about as often as you'd expect to run into things with fire damage resistance. Or just change the resistance from fire to necrotic. It's hardly game breaking though.
You could even flavor it without changing the type of damage. It's magic and you are limited only by your imagination. Cold fire can absolutely be a thing.
I've often felt that the "gamble" of Fireball was often less the fact that fire is so frequently resisted (although that's obviously a problem as well) so much as the collateral damage that results. There are a lot of environments where Fireball just isn't an option because of the risk of starting a huge fire or damaging an important structure. I think, whatever type you change the spell to, you should consider how it will interact with the environment. If there's no risk for the spell when used in, say... a library, then it's just a 100% improvement over Fireball at no additional cost. I'm also a fan of altering the spell a bit to give it additional effects... like maybe reduce the damage to 7d6 Cold or Necrotic but add in the detail that creatures that fail their save have their max speed reduced by 10 for the next round or something like that.
After looking at resistance distributions, I think I'll change it to Cold (rather than necrotic). I saw that more monsters (in the MM at least) have cold resistance than fire. And there are about half as many with cold vulnerability than fire. Though there are more with fire IMMUNITY but that's pretty much limited to Fire-based Dragons and elementals (which aren't a focus in my current campaign).
In fact, one of the more prolific monster categories in my campaign are fiends which quite often HAVE cold resistance. So I think just switching the damage type to Cold from Fire would actually be a bit of a nerf in terms of resistances and the trade off would be less collateral damage than your typical fireball.
OR I could just say "They're edgy black shadow flames" and leave the spell alone xD
Regarding preserving the collateral damage element, you could make it age everything. I.e. if you are on the second floor, and you cast necro-ball, it ages the floor boards. Crossing those boards now requires an athletics check - failure results in a fall to the floor below with 1d4 bludgeoning damage (changed from regular fall damage to match standard fire damage - hand wave it that the floor collapses slowly enough to slow your fall but you still reacted to slowly to move in time).
The 'necro-rot' could spread precisely how a DM may rule fire spreading, with similar effects. If it spreads to a support pillar, you're now at risk of a ceiling collapse. Similar to fire, wood is far more at risk of aging than stone, so it would make the spell very similar.
So I have a player with a shadow sorcerer in my current campaign and she has picked spells that deal cold and necrotic damage over some of the higher damaging fire/lightning spells in order to fit the flavor of her backstory/origin.
I know she wants to be a Blaster character and 5th level is coming up quicker than anticipated and I know fireball is on its way. I was thinking of giving her a modified fireball that deals necrotic (or cold) damage INSTEAD of fire to better match the theme. I know Tasha's gave a new metamagic that lets sorcs change the damage type of spells, but I don't want her to have to spend a SP every time just to fit theme.
I don't imagine switching fire damage for necrotic (or cold) would cause to many issues, both of them are on par with fire in terms of monster resistances so I don't think I've made the spell "better" just different. But I also know I could be overlooking something.
Does this seem fine?
Rule 0 - everything is at your discretion.
In terms of balance, the thing to watch with changing the damage type is how common the resistance is. I'm not totally sure, but I think resistance to necrotic damage is rarer than resistance to fire damage. That's why many people thing thunder damage is superior - resistance is rare. So there's a small shift in the player's favor there. But you just need to make sure that they are running into things with necrotic damage about as often as you'd expect to run into things with fire damage resistance. Or just change the resistance from fire to necrotic. It's hardly game breaking though.
You could even flavor it without changing the type of damage. It's magic and you are limited only by your imagination. Cold fire can absolutely be a thing.
I've often felt that the "gamble" of Fireball was often less the fact that fire is so frequently resisted (although that's obviously a problem as well) so much as the collateral damage that results. There are a lot of environments where Fireball just isn't an option because of the risk of starting a huge fire or damaging an important structure. I think, whatever type you change the spell to, you should consider how it will interact with the environment. If there's no risk for the spell when used in, say... a library, then it's just a 100% improvement over Fireball at no additional cost. I'm also a fan of altering the spell a bit to give it additional effects... like maybe reduce the damage to 7d6 Cold or Necrotic but add in the detail that creatures that fail their save have their max speed reduced by 10 for the next round or something like that.
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After looking at resistance distributions, I think I'll change it to Cold (rather than necrotic).
I saw that more monsters (in the MM at least) have cold resistance than fire. And there are about half as many with cold vulnerability than fire. Though there are more with fire IMMUNITY but that's pretty much limited to Fire-based Dragons and elementals (which aren't a focus in my current campaign).
In fact, one of the more prolific monster categories in my campaign are fiends which quite often HAVE cold resistance.
So I think just switching the damage type to Cold from Fire would actually be a bit of a nerf in terms of resistances and the trade off would be less collateral damage than your typical fireball.
OR I could just say "They're edgy black shadow flames" and leave the spell alone xD
Regarding preserving the collateral damage element, you could make it age everything. I.e. if you are on the second floor, and you cast necro-ball, it ages the floor boards. Crossing those boards now requires an athletics check - failure results in a fall to the floor below with 1d4 bludgeoning damage (changed from regular fall damage to match standard fire damage - hand wave it that the floor collapses slowly enough to slow your fall but you still reacted to slowly to move in time).
The 'necro-rot' could spread precisely how a DM may rule fire spreading, with similar effects. If it spreads to a support pillar, you're now at risk of a ceiling collapse. Similar to fire, wood is far more at risk of aging than stone, so it would make the spell very similar.
Just spitballing.