Fun with D&D 5 Magic: Fireball

You know where this is going, so let's start off with a bang.

Fireball creates a 20-foot radius flaming explosion that "spreads around corners." Let's assume for a moment this is the old-school fireball, and it fills a volume. A 20-foot radius sphere is 33,510 cubic feet of fireball, or about 34 ten-foot cubes of 1,000 cubic feet each.

Let's cast this into a 20x20 room with a 10-foot ceiling. That's just 4 of our 34 cubes used up. The rest of those thirty squares of fireball have to go somewhere, right? Let's assume there are three ten foot wide and high halls coming out of this room, doors or not those will likely get blown off so let's treat them all equally. Three halls among our thirty remaining cubes of fire equal ten cubes each, so we can assume each one of those hallways is getting a 100-foot long fireball racing down their length.

Boom, I hope you weren't casually throwing that fireball into the room from 60-feet down the hall, otherwise, you and your party are getting too close to the grill today.

Now, the one strange part of the spell is that it says it ignites flammable objects in the area that aren't being "worn or carried" - so if you are carrying vials of oil, flammable parchment, bundles of dry moss, firecrackers, TNT, or open containers of gasoline, you are safe. In this game, not in real life, so don't try this at home!

Geeze, people.

Wow, this is a major pull back from AD&D 1st Edition, where if you were following the rules, you started making saving throws for every exposed piece of gear, magic items, armor, and weapon in your party You could lose your backpacks and have that treasure go all over hell, your scrolls could burn up, you could lose that +3 longsword, the cloak of elven-kind was probably toast-ed-kind, and you were sitting there making saves for rings when all was said and done.

To me? D&D 5 brought this old-school wraith upon itself, and I am forcing spell DC saving throws for all exposed gear. Go cry in your D&D 4 books, retro is cool nowadays. Stuff that is resistant to fire (metal, gems, asbestos) gets advantage on the roll, while fragile and flammable stuff (scrolls, glass, gunpowder, cloth) is getting disadvantage. Ignitable items that fail saves are getting burned up like smores dropped into a bonfire, and explosives are going boom-boom for full rolled damage to those stupid enough to carry gunpowder with a trigger happy fire mage in the party.

Smoke? Yes smoke, if fires are set or dungeon furniture was burned up. Too bad there are no rules for smoke or choking in the rules, so it's DM fiat time. In every square affected for the next 10 to 30 minutes, CON Save or take 1d6 damage, plus heavy obscurement and blindness if the smoke is acrid enough. If the dungeon is small enough and there's enough to burn, I will just fill the whole place with smoke and start to up the damage as the oxygen depletes to a d12 on a failed save or something.

Locked doors may be destroyed, and the treasure and furniture of the room will need saving throws, so there may not be much left in there after you nuke it from orbit. Traps may also be destroyed, so have those makes saves too. If a door makes a save, save those squares of fireball and have them go somewhere else! That door is also probably stuck beyond repair too having survived an explosion like that.

If I am feeling particularly nasty, structural damage may come into play. If this is an old and structurally unsound dungeon, tomb, or cave, I may have affected areas make spell DC saves or collapse. Don't forget localized damage to door frames, arches, statues, stairs, fountains, levers, mechanical devices, or other items character may have needed to use to solve the adventure.

Oh, and if you think that an explosion in a small space that if outdoors would be heard for miles isn't going to wake the dead, rest assured the entire map is going to hear this and start sending monsters to check out the carnage. They could also send others to investigate, and you better pray to one of the pantheon of deities they don't have a fireball to shock-and-awe you to return the favor. What's good for the monsters is good for the party, and my monsters don't pull punches.

Sooty the Owlbear says, only you...would be so stupid to cast a fireball in an exposed space.