Mazirian stroked his chin. Apparently he must capture the girl himself. Later, when black night lay across the forest, he would seek through his books for spell to guard him through the unpredictable glades. They would be poignant corrosive spells, of such nature that one would daunt the brain of an ordinary man and two render him mad. Mazirian, by dint of stringent exercise, could encompass four of the most formidable, or six of the lesser spells.

— Jack Vance, The Dying Earth, Chapter 2: “Mazirian the Magician”

Standard magic in TSR D&D is based loosely on the way magic works in The Dying Earth stories by Jack Vance (and others) in that casters must memorize their spells and they forget them when cast. However, the spells in D&D are generally weaker than those in Vance’s stories, there were many more “levels” of spells, and powerful caster’s could memorize large numbers of them. When we switched to a spell point system with my Body Point and Hit Point rules, one of my players, who was a Dying Earth fan, suggested adding a separate class, the Mnemonic Mage, which would be somewhat closer to Vance’s actual system as an alternative magic-user. After comparing the mages in The Dying Earth (at least those where the stories mentioned the number of spells they could hold in their minds), we decided that Mazirian was an 11th level character and built the system around that. Turning D&D’s nine levels of spells into two simply did not work, so we ended up with five.

Amazingly, the class worked well. Mnemonic mages could memorize only a very small number of spells, but they had access to more powerful spells right off the bat — assuming they had them in their spell books, of course. Unfortunately, the class would probably not be popular among modern D&D players as a Mnemonic mage runs out of spells very quickly if played like a combat machine and would therefore be considered “useless” by many and require a “15 minute workday” to be playable. Old school players should not have this problem so I’ve decided to include this class in the Optional Rules section of Tarnhelm’s Terrible Tome. The complete version will be there, but here is the essence of the spell memorization part of the system.

A Mnemonic Mage has his level + 1 memory slots.

Spells are divided into groups that require different numbers of memory slots to hold in memory:

Minor Spells – 1 memory slot (1st and 2nd level magic-user spells)
Lesser Spells – 2 memory slots (3rd and 4th level magic-user spells)
Greater Spells – 3 memory slots (5th and 6th level magic-user spells)
Extraordinary Spells – 5 memory slots (7th and 8th level magic-user spells)
Most Extraordinary spells – 10 memory slots (9th level magic-user spells)

Assuming Mazirian is 11th level in this system, he would have 12 memory slots which would allow his mind to hold 4 Greater Spells or 6 Lesser spells — just as he can in Vance’s story.

1st level mages start with spell books holding 3 minor, 2 lesser, and 1 greater spell. The player may select two of the minor spells, the others are selected by the GM by whatever method he wishes. Of course, they only have 2 memory slots at first level so their minds can only hold 2 minor or one lesser spell.