Spellcasters have two main limits:
- **How many spells they can cast**
- **How many spells they can maintain at once**
These are handled by **Spell Slots** and **Concentration**.
#### Spell Slots (Your Magical Fuel)
Spell slots represent **how much magical energy** you have.
Casting a spell **uses a slot** of that spell’s level or higher.
##### The Core Rule
> **Spells are what you know.
> Spell slots are how often you can use them.**
#### 🎯 How Spell Slots Work
- Each spell has a **level** (1st, 2nd, 3rd, etc.)
- You must spend a spell slot **equal to or higher** than the spell’s level
- Once a slot is used, it’s gone until you rest
Example:
- _Fireball_ is a 3rd-level spell
- You can cast it using:
- A 3rd-level slot
- A 4th-level slot
- A 5th-level slot
#### Casting at Higher Levels
Some spells get stronger if cast with a higher slot.
This is written in the spell description as **“At Higher Levels”**.
Example:
- More damage
- More targets
- Longer duration
#### Getting Spell Slots Back
- **Long Rest** → all spell slots return
- **Short Rest** → some classes recover limited slots
Spell slots are precious — manage them wisely.
#### Cantrips (Free Spells)
Cantrips are:
- Level 0 spells
- Unlimited use
- Scale automatically as you level
Example:
- _Fire Bolt_
- _Guidance_
- _Sacred Flame_
Note: Cantrips **never use spell slots**.
#### Common Beginner Confusion (Important!)
Spell **level** is **not** character level.
A 5th-level wizard:
- Has access to 3rd-level spells
- Still has 1st-level spells
- Uses different spell slots for each
#### Concentration
Some spells require **Concentration**.
This means:
- You must focus to keep the spell active
- You can only concentrate on **one spell at a time**
#### The Core Rule
> **You can only concentrate on one spell at once.**
#### When Concentration Is Required
If a spell says **“Concentration”**:
- It lasts until:
- The duration ends
- You drop concentration
- You lose concentration
#### What Breaks Concentration?
You lose concentration if:
- You cast another concentration spell
- You take damage and fail a check
- You become incapacitated
- You choose to end it (no action required)
#### Concentration Checks
When you take damage:
- Make a **Constitution saving throw**
- DC = **10 or half the damage**, whichever is higher
Fail → spell ends
Succeed → spell continues
#### Concentration & Multiple Effects
You **cannot**:
- Maintain two concentration spells
- Stack multiple powerful buffs
Casting a new concentration spell **immediately ends** the old one.
#### DM Rule of Thumb
> **If a spell controls, restrains, or buffs over time, it probably requires concentration.**
#### Summary
> **Spell slots limit how many spells you can cast.
> Concentration limits how many you can keep going.**
#### 🧠 Quick Reference
|Concept|Limit|
|---|---|
|Spell Slots|Uses per rest|
|Cantrips|Unlimited|
|Concentration|1 spell|
|Slot Level|Spell level or higher|