Regardless of how many spells a caster knows or prepares, he or she can cast only a limited number of spells safely before resting. Manipulating the fabric of magic and channeling its energy into even a simple spell is physically and mentally taxing, and higher-level spells are even more so.
As players level up they can learn more spells and can use more of their magic to empower those spells to make them stronger. However, the source of magic/access to the magic matrix is not unlimited and can run out. Mechanically this works by gaining a point of casting exhaustion. Creatures will gain levels of Casting Exhaustion from repeated use of spells without rest or without proper safety or knowledge of the spell.
Think of it like a mana meter. The closer you are to empty, the more difficult to cast spells will be. Once depleted, you no longer can cast spells. As you level up however, the mana meter grows larger meaning you can cast more spells and at higher levels before resting.
Exhaustion Effects
| Level | Effect |
|---|---|
| 1 | Disadvantage on non-cantrip spell attacks. DC 10 Arcana Check on non-cantrip spells to not misfire. Backfire on nat 1. |
| 2 | Cantrips DC 10 misfire. Backfire on all spells on nat 1, 2, and 3. |
| 3 | Higher spells require DC 15 Arcana Check or spell will misfire. |
| 4 | All damage from spell attacks halved. Chance to damage a player’s ability to cast spells in the future (-x on spells). |
| 5 | All spells must use HP to cast. Must succeed a DC 13 CON saving throw or suffer permanent damage such as scars or disfiguration. |
| 6 | Lost connection and control of the fabric of magic. Grants the option for cool role playing moments. Can also be a dice roll or coin flip type of deal. |
A creature suffers the effect of its current level of exhaustion, as well as all lower levels.
Long rests will cleanse 1 point of casting exhaustion, assuming that the creature also has regular food and water to drink.