So Fireball makes a 20ft radius sphere.
That’s a sphere with a volume of 33,510.322 ft^3
A sphere 100 times bigger would be 3,351,032.2 ft^3
Such a sphere would have a radius of 92.832ft
The range of fireball is 150ft, so you could safely cast it’s 100x magnitude counterpart.
Of course this is a very simplified idea of what 100x magnitude fireball could do. For instance, does it do 100x the fire damage? ~2,800? That’s over 50.9x more than lava (which is ~55). Does that mean it’s 50.9x hotter than lava? Making it 35,630-61,080 C, 6-11x hotter than the surface of the sun?
These calculations are all fast and loose as actual explosion calculations are too complicated for my little brain.
If a massive fireball hits you, just shout “I do not consent!” If someone who will survive the blast hears you, they are required to spread the story at every tavern they go to.
The slight DM pedant in me is torn about how you chose to interpret the size of the sphere.
There is absolutely no reason to not use volume as the thing being modified by the item EXCEPT as far as I am aware the RAW is that the fireball is measured by its radius.
By that reasoning the new fireball should have a radius of 200 ft.
Which is obscenely large and also puts the caster within the blast radius.
If I remember correctly in older editions the fireball would also fill up rooms until it's full VOLUME was achieved not necessarily just it's radius.
Meaning a 20ft radius fireball would fill a 5ft x 5ft hallway/tunnel (weird size I know... easy math) for 1,340ft and the new 200ft radius (33,510,300 ft^3) fireball would fill the same hallway for... 1,340,412 FEET OR JUST SHORT OF 254 MILES OF TUNNEL!
If my players were stupid enough cat fireball on a magic enhancing object, personally, I'm using the later object and also multiplying the damage by 100.
Their new party can start by investigating the massive village size crater recently discovered by the locals.
In 5e evocation wizards get an ability that allows them to choose up to 1 + the spells level friendly targets that are unaffected by an evocation spell. This makes several of these large area of effect spells safe to use.
Such a sphere would have a radius of 92.832ft
The range of fireball is 150ft, so you could safely cast it’s 100x magnitude counterpart.
Maybe I'm stupid but I don't see how you could safely cast it. Even if you cast it all the way back at the edge of the range you still would be inside the radius.
The radius is the size of the sphere as measured from the center of the explosion.
Maybe this analogy helps.
You throw a ball at a wall and it bounces back towards you. If the ball reaches you or passes you then you die.
You can throw a ball (the fireball) 150ft.
At the end of your throw it hits a wall (center of explosion). The ball bounces back towards you 92.832ft (explosion radius/edge of explosion). The ball is now 57.168 ft away from you. Ball did not reach you therefore you live.
If you cast it so that it’s point of origin is 150ft away from you, then it would expand both 93ft towards you and 93ft away from you. By expanding 93ft towards you, there’d still be a gap of 57ft between you and the edge of the fireball. The farthest point edge of the fireball would be 243ft away.