“I cast Fireball!” – A Spellcasting Guide

“I cast Fireball!” is pretty straightforward in terms of interpretation, right? The caster wants to incinerate everything in a 20 foot radius for 8d6 fire damage. Fireball is not a pretentious spell. It doesn’t come with a wall of text explaining what it does. It costs an action and a 3rd level spell slot. Super straightforward, until it gets mired in spellcasting rules.

Some hypotheticals about casting Fireball:

  • A 9th level warlock casts Fireball, but it does more damage than the wizard’s Fireball. 
  • An artificer is the same level as the wizard, but still cannot cast Fireball.
  • A sorcerer manages to cast both a Fireball and Poison Spray in one turn.
  • A player with two levels in fighter and 5 in wizard manages to cast two Fireballs in one turn!

Spellcasting is one of the more challenging concepts for new players and Dungeon Masters. Issues arise not only from the complexity of individual spells, but the rules surrounding spells in general. For starters, classes experience spells in different ways. We’ll cover a few details about spellcasting before moving on to Fireball.

Preparing Spells

Certain classes pick up spells as they progress through their levels and use them innately. These classes do not prepare spells and, as such, have a limited pool of spells to draw on (with other abilities to make them unique). Other classes prepare their spells from the full spell list of that class. It doesn’t stop there either, certain classes can prepare less spells than others. Here is a breakdown:

Innate Casters:

  • Bard
  • Sorcerer
  • Warlock

These classes pick spells to learn at each level. Once they learn a spell, they usually cannot change it. They are stuck with it for the rest of their casting career.

Full Casters:

  • Cleric
  • Druid
  • Wizard

Full casters prepare spells from their class spell list. They can prepare a number of spells each day equal to their level plus their casting modifier. For example, a level 3 Druid with a +3 Wisdom modifier can prepare 6 spells each day. 

Half Casters:

  • Artificer
  • Paladin
  • Ranger

Half casters prepare spells from their class spell list. They can prepare a number of spells each day equal to half their level (rounded down) plus their casting modifier. For example, a level 3 Paladin with a +3 Charisma modifier can prepare 4 spells each day. 

Spell Slots

To use a warn out analogy, spell slots are like the ammo of the spellcasting world. When a caster runs out of spell slots, they cannot use any spells beyond cantrips until they finish a long rest. Spell slots grow as classes level up. A full caster, such as a wizard, can cast a 3rd level spell when they reach the 5th level. That brings us to Fireball.


3rd level spell

Casting time: One action 

Range: 150 ft.

A bright streak flashes from your pointing finger to a point you choose within range then blossoms with a low roar into an explosion of flame. Each creature in a 20-foot radius must make a Dexterity saving throw. A target takes 8d6 fire damage on a failed save, or half as much damage on a successful one. 

The fire spreads around corners. It ignites flammable objects in the area that aren’t being worn or carried.

Fireball is perhaps the most iconic spell in Dungeons and Dragons. It offers above average damage for a 3rd level spell in a large radius. Group of goblins charging towards the town? Fireball. Pirate ship closing in on the trade vessel you were paid to protect? Fireball. Negotiations breakdown during a hostage situation? Fireball. Minor disagreement with the magic store clerk over the price of incense? Fireball.

Disregarding how amazing Fireball is for absolutely every situation, it is a great teaching tool for spellcasting mechanics. Let’s break down a few of the nuances of spellcasting using Fireball. Metamagic, Pact Magic, and Action Surge alter Fireball in exciting ways.


Sorcerers come with a potent feature called Metamagic. As of the release of Tasha’s Cauldron of Everything, each class can gain some Metamagic features by taking a feat. Metamagic alters spells in unique ways. The most commonly misunderstood Metamagic feature is Quickened Spell.

Quickened Spell

When you cast a spell that has a casting time of 1 action, you can spend 2 sorcery points to change the casting time to 1 bonus action for this casting.

At face value, this sounds very powerful in the context of Fireball. If I cast Fireball as a bonus action, I still have an action left to cast, you guessed it, another Fireball! Sadly, this is an incorrect assumption. D&D has a strange quirk when it comes to spells cast as bonus actions. Specifically:

“A spell cast with a bonus action is especially swift. You must use a bonus action on your turn to cast the spell,

provided that you haven’t already taken a bonus action this turn. You can’t cast another spell during the same turn, except for a cantrip with a casting time of 1 action.”

  • Player’s Handbook p.202

Effectively, if you cast Fireball as a bonus action, you cannot cast another Fireball on the same turn. Quickened spell does not negate this rule. At most, you could cast a cantrip like Fireball’s lesser brother, Firebolt. If Fireball was Chris Hemsworth, Firebolt would be Liam. 

While it isn’t two Fireballs, freeing up an action with Quickened Spell provides a lot of tactical options. It allows the a character to do any of the following actions:

  • Attack with a weapon.
  • Dash at double speed.
  • Disengage safely from an enemy.
  • Dodge attacks.
  • Help another character.

All of these options can provide a significant edge to a caster using Metamagic. Additionally, edging out some damage or providing much needed utility with a cantrip can save the day in certain situations. Imagine holding back a tide of orcs with a Fireball while your Rogue friend picks the lock to a door you need to escape through. You cast Guidance on the same turn, giving the Rogue the boost they need to pick the lock and get you to safety. 

Pact Magic

Warlocks possess a unique spellcasting feature called Pact Magic. They draw their powers from magical sugar daddies (Patrons) that possess unique abilities. For a warlock to gain access to Fireball it chooses the Fiend patron and can choose the spell at 5th level. So how does Pact Magic work?

Warlocks have a very limited number of spell slots compared to other casters, topping out at 4 total at level 17. To balance this shortfall, warlock spell slots recover after a short rest instead of a long rest. Additionally, they have another unique feature: they are always cast at the highest level. 

Warlocks are like sprinters in a world of spellcasting where everyone else runs marathons. Their spells go fast and hard. For instance, a level 5 warlock casts Fireball at 3rd level using a spell slot. However, at level 7, the warlock casts Fireball using a 4th level spell slot. This change increases again at level 9.

Even though warlocks only have two spell slots until they reach level 11, those spell slots increase in power. The spell level caps out at 5th level spell slots. This means that a level 9 warlock casting Fireball does 10d6 fire damage. Pretty hot. 

Action Surge

Now onto the reason spellcasters take a multiclass dip into the fighter class. At level 2, fighters gain a powerful feature called Action Surge. The uses of this ability act like Quickened Spell without the limitations. For a fighter, it usually means they get to make twice the number of attacks. Casters have a different interest in this ability. 

“Action Surge

Starting at 2nd level, You can push yourself beyond your normal limits for a moment. On your turn, you can take

one additional action on top of your regular action and a possible bonus action.”

  • Player’s Handbook p.72

This means what you think it means. The holy grail. Two Fireballs in a single turn – 16d6 fire damage. Because Action Surge creates an additional action, casters are free to double up on spells once per short rest. If they chose fighter to start with, they gain the added armour and Constitution saves fighters enjoy. 

So there you have a few of the more nuanced spellcasting mechanics. Each subject we have touched on can be explored more in depth. Pact Magic and Metamagic have a lot more going on than just Fireball. Action Surge also brings up a conversation about just what can be done on a single turn. All of these subjects will be discussed in future articles. For now, enjoy Fireballing!

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