A longterm pet peeve of mine from earlier versions of D&D that still finds grievance in 5th edition is that given the choice between learning fireball or lightning bolt you’d have to be crazy to opt for the latter. Whilst both do the same amount of damage (a hefty 8d6 to anyone in the area of effect, dex. save for half), fireball can be flung up to 150 feet and affects all those in a 20 foot radius (surface area = 1256 ft.). Lightning bolt emanates from your hands extending in a line 100 feet long and 5 feet wide (surface area = 500 ft). Basically, unless you plan on attacking a marching band, fireball is going to fry significantly more bad guys every time.
This for me equates to poor game design. If there’s no real choice to be made between two options then what’s the point in having two options instead of one? Even the major drawback of fireball – the fact that it sets alight flammable objects in the area that aren’t being worn or carried, is mimicked by lightning bolt, meaning there’s very few contexts indeed where the latter is more useful (facing creatures who are immune / resistant to fire would be the only really obvious one).
Evening Up The Score
How do I fix this as a DM and give PCs a real choice to make when choosing to learn / prepare one of the two spells over the other? Well one simple solution would be to reduce the damage of fireball to either 6 or 7d6 damage, a solution I rather like as the spell’s excessive damage is basically a mistake (it should probably be a 5th or 6th level spell!), that unbalances the game. However it’s a mistake that gamers loved so much that it stuck around (DM David has some interesting related reading on this topic).
If you’re a bit nervous about messing around too much with the damage of the game’s most iconic spell, then what you could do instead is pimp lightning bolt a bit by giving enemies in metal armour disadvantage on their saving throw when struck. A small change that makes a lot of sense in terms of realism and in the right circumstances could make lightning bolt even deadlier than fireball – and therefore a viable choice.
You could also rule that fireball alone sets alight flammable objects, giving lightning bolt two pros to balance the twin cons of a much more limited range and much smaller area of effect.
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