1. Origins: Vancian Magic (OD&D and AD&D)
D&D's original magic system is often referred to as "Vancian magic," named after the author Jack Vance, whose works inspired it. In this system, magic-users (later called wizards) prepare spells in advance and forget them once cast.
Original Dungeons & Dragons (OD&D) (1974): The earliest editions of D&D, including the original 1974 release, used a Vancian system where characters had a number of spells they could prepare and cast per day.
Advanced Dungeons & Dragons (AD&D) (1977-1979): This system was solidified in AD&D, where magic-users and clerics had spell tables dictating the number of spells of each level they could prepare and cast each day.
2. Transition to Spell Slots (D&D 3rd Edition)
The first notable shift towards a spell slot-like system occurred with the introduction of new classes in D&D 3rd Edition.
Dungeons & Dragons 3rd Edition (2000): This edition introduced Sorcerers and Bards, who used a system more akin to spell slots as we understand them today. These classes could cast a number of spells per day from a list of known spells, using slots of specific levels. This system allowed for more flexibility compared to traditional Vancian magic.
3. Refinement and Expansion (D&D 3.5 and 4th Edition)
The concept of spell slots was further refined and expanded in subsequent editions.
Dungeons & Dragons 3.5 Edition (2003): The 3.5 revision continued to use the spell slot system for Sorcerers and Bards, while Wizards and Clerics largely retained their Vancian preparation.
Dungeons & Dragons 4th Edition (2008): This edition overhauled the magic system entirely, moving away from Vancian preparation to a unified power system where all classes had "powers" that could be used a certain number of times per day, per encounter, or at-will. While not exactly spell slots, this system emphasized flexibility and resource management.
4. Modern System (D&D 5th Edition)
D&D 5th Edition blended elements of Vancian magic and spell slots, creating a more streamlined and flexible system.
Dungeons & Dragons 5th Edition (2014): In this edition, all spellcasting classes use spell slots to cast spells. Spellcasters prepare a list of spells each day (for classes like Wizards) or know a set number of spells (for classes like Sorcerers), and they use spell slots to cast these spells. This edition also introduced the concept of upcasting, where spell slots of higher levels can be used to cast lower-level spells with enhanced effects.