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TTRPG: How magic works in D&D 5e

So you want to play a caster? It can be pretty overwhelming when you start to look into it. Spell casting modifier? Spell slots?! SPELL PREPERATION?! SPELL SAVE DCS?!?!?! WHAT?

I’ll be happy to help pick this apart for you and I’ll try my best to keep it simple. We’ll start with the basic frame work, gloss over schools of magic, break down the jargon used, and cover spell lists and spell prep. I’m hoping this will make sense for you. However, if by the time you get to the end of this blog it still doesn’t make sense, please drop your questions in the comments, or come and ask me directly on Discord! (A link to our server is on the home page of this website!)


Spell caster -> You have a Spell List -> You prepare spells from your list -> Throughout the day you have resources called Spell Slots that you can use to cast your spells -> Long rest and reset your resources.

That’s the frame work and grossly simplified, especially as there are exceptions depending on class. BUT I will go over that below.

There are 8 types, or “schools,” of magic in D&D 5e. Abjuration, Divination, Illusion, Evocation, Enchantment, Conjuration, Necromancy, and Transmutation. This is less important when learning how to play a caster, but is just an aside that you can come back to later (especially if you use the “Identify” spell). If you’d like to learn about them, the most straightforward way is to have a look at the Wizard class in the player’s handbook. As a wizard, you pick your school of magic at second level. It has them listed and some simple definitions.


Spell Casting Modifier:

Before getting into what it is, it’s helpful to know that when you cast a spell that affects another creature, one of two rolls will happen. You will do a spell attack (d20+Spell Attack Bonus) or your target will do a saving through (d20+MOD vs. your Spell Save DC). The spell attack bonus is simply your Spell Casting Modifier plus your Proficiency bonus. I’ll cover Spell Save DCs shortly.

If it requires it, a spell will say “add your spell casting modifier” in the description (e.g.- “Cure Wounds”). And as I just mentioned, when you do an Attack, it’s your Spell Casting Modifier PLUS your proficiency bonus; pretty much like a dex or strength-based attack with a normal weapon. You’re just using your brain power instead. So where do you find it?!

It’s just one of your stats.

Your spell casting modifier is the stat your class uses to cast magic.

Wizards use Intelligence.

Druids, Rangers, and Clerics use Wisdom.

Bards, Sorcerers, Paladins, and Warlocks use Charisma.

For instance!

My sorcerer’s charisma modifier is +4 (sweet!). So my sorcerer’s Spell Casting Modifier is +4, because sorcerers are a Charisma-based caster! And if my sorcerer uses their freaky-deaky Chill Touch cantrip, which us a ranged spell attack, I’ll roll my fancy metal d20…*rolls*…. and I rolled a 12! Cool! Then I add my Spell Casting Mod/CHA (+4) and my proficiency bonus (+2)….For a total of 18! That’s a pretty sweet hit. Roll damage and move on.

This modifier is used throughout, but now you know what it is, so should’ve be too bad, right?

Spell Save DC:

This number also uses the Spell Casting Modifier and is used when casting area of affect spells, enchantment spells, etc. Anytime it asks for a target to do a saving throw, it is against this number. To get this number is 8+Spell Casting Modifier+Proficiency Bonus. So for my Sorcerer it would be 8+4+2 = 14

So if she’d cast Charm Person, the target would roll a wisdom saving throw to resist, needing to roll a 14 or higher on their d20. If they get 13 or lower, then I’ve successfully charmed them.

Spell lists! Spell slots! Spell prep! OH MY

Spell list: Each class has their own list of spells that you as a player get to choose from as you level up. Here’s an example of a small part. It’s important to know that spells have their own level system. Just because you are a level 2 spell caster doesn’t mean you can use a level 2 spell. The spells you do have access to will be determined by what spell slots you currently have, according to your class level.

To find out what spell slots you have, you look at your class’s level chart (example below). The chart shows what spell slots you get and at what level. Again, the spell level you have access to will match what level spell slots you have. FOR INSTANCE, using the Wizard chart, at level 2 you have access to level 1 spells (because you have three level 1 spell slots). Then at level 3 you’ll be able to pick a level 2 spell, now having access to two level 2 spell slots. BUT WHAT ARE SPELL SLOTS?!

Spell slots are just a resource. It’s how you can cast your spell. A level 2 spell can only fit into a level 2 spell slot (or higher). It can’t fit into a level 1 spell slot (too small!). The bigger (or higher level) the spell slot, the more powerful the spell. So if you cast a level 2 spell with a level 3 spell slot, you could be making it stronger! BUT you won’t know that unless you….


This is so so so so so so so so so so so so important if you’re going to play a caster. Your DM isn’t in charge of your character, class, or spells. Don’t rely on them to know how it all works. That’s your job (they have enough going on, I promise you). You need to be aware of how long spells take to cast (1 action vs 1 minute vs 10 minutes, etc), whether they take concentration (you can only have 1 concentration spell up at a time, and will need to do a CON save should you take damage in order to maintain your concentration), and ultimately what the spell even does! Reading your spells and understanding them will make you a more effective player. And if it’s confusing, just ask! You don’t need to know how everything works right away. You will learn and get better the more you play.


These are your bread and butter as a caster. You do not need a spell slot to cast these. You can cast them as much as you want! It’s always good to pick at least one damage-dealing cantrip if you’re a full caster (less important for those who mostly use phsyical weapons). These also don’t count against your prepared spells for the day, if you have to prep spells that is. Which will take me to talking about specific classes…

Prepping Spells from a Spell List

Wizards, Clerics, Druids, and Paladins can prepare their spell list from a larger list of spells. Wizards have a spell book that they carry around. They are unique in that they can copy spell scrolls into their book and can add to their list between levelling up. Paladins, Clerics and Druids get access to their class’s spell list in its entirity! The number of spells that a character can prepare for the day is the Spell Casting Modifier + Class Level (Paladins=1/2 Level). Every long rest, you can swap spells out.

Sorcerers, Bards, Warlocks, and Rangers have their list of spells all the time, which is added to when they level up. No daily prep needed.

And that’s all I’ll be writing about for today! Phew! Please drop any questions in the comments! Happy to talk about casting and the details of it. I mostly play casters, anyway, and have been known to learn new things. If you’re new to D&D or TTRPGs and are looking for a place to play, check out the events page and please come join us on our Discord Server! We’ve new games going up all the time and are happy to teach folks to play. If you’re looking to learn how to run games or already do, you’re welcome to do that with us too!

In the mean time, have fun guys and see you at the table!

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