Finite Energy

Magic is unlimited, but your ability to channel it is. Spellcasters can initially cast a number of cantrips equal to their proficiency bonus plus their key ability modifier. Cantrip slots are restored after a short or long rest.

At each even-numbered level, characters gain an additional cantrip slot in addition to any increases which come from an increased proficiency bonus and/or key ability modifier. For example, a level 10 wizard with an Intelligence score of 18 would be able to cast her cantrips up to 13 times without needing to take a short rest: 4 from her key ability modifier, 4 from her proficiency bonus, and 5 more from character levels. If creating a character at a level higher than 1st, your number of cantrips per rest is equal to your proficiency bonus plus key ability modifier plus half your character level (rounded down, as is always the case).

Cantrip slot increases occur regardless of the class which is raised, meaning that the number of uses increases even for those characters who do not have a spellcasting class, such as an elven fighter who has only a single cantrip granted by his heritage.

Added to House Rules in 2023; modified 9 April 2024 to allow for slot increases with level advancement.