The idea would be to create a book that offers a variety of different approaches to magic, with expanded options for the existing magic systems and a heap of new options that allow you to customise the system to your own needs.
Here are some of the things that I would love to see in such a book:
- Rules options for tailoring the magic system outlined in the core rulebook to the most common campaign styles (high fantasy, swords & sorcery, dark fantasy, historical fantasy, steampunk, et al). This would explicitly address the needs of low magic campaigns as well as those campaigns that wish to incorporate world-shaking epic magic. Perhaps it might be possible to touch on such common fantasy tropes as Old Magic that is more powerful than existing forms of magic, but also more difficult to control.
- A selection of Common Magic spells that move beyond combat-oriented spells and reflect the kind of powers possessed by hedge wizards in folklore and fantasy. This would introduce spells such as Evil Eye, Create Protective Amulet, Love Spell, Bless Hearth, Increase Fertility, etc.
- An expanded divine magic spell list that reworks some of the existing material from Cults of Glorantha to remove the setting-specific content. Spells such as Celestial Divination, Counter Undead, Fateful Omen, Festival Ritual, etc could fit into just about any fantasy setting with ease.
- Rules for magic schools in the vein of Harry Potter, Ursula Le Guin's Earthsea series, Terry Pratchett's Unseen University, et al.
- A system for resolving formal spell duels between rival wizards in the vein of T.H. White's Sword in the Stone
- Rules for libraries and arcane research. Every wizard should need to consult the books occasionally!
- Expanded rules for Ceremonial Magic that build on the communal magic rules presented in Spellcom. This is an important fantasy trope and begs for expansion - how often do spellcasters conduct arcane rituals in fiction and how often do groups of spellcasters combine their powers to achieve some effect that is beyond the capabilities of any individual? A critical failure with ceremonial magic should be very risky - for example, ambitious groups of sorcerers who attempt to use ceremonial magic summon a powerful demon might discover that they can't control it when it arrives And remember the fate suffered by the Witches of Estacerp in Andre Norton's Witch World novels - one mistake at a vital point in the ritual and all of the nation's spellcasters were wiped out, leading to a shift in the balance of political power!
- Expanded rules for demonology (building on the rules provided in Elric and Spellcom. There is also a need for a divine magic equivalent, offering information on demon-worhippers and their infernal powers.
- Expanded rules for necromancy that clean up the best material from Nectromantic Arts.
- New rules for Lovecraftian sorcery, possibly adapting some material from the defunct Conan product line. This would introduce a Blasphemous Lore skill and rules for summoning and binding eldritch horrors from beyond space and time. There might also be room for some guidelines on Forbidden Cults and Elder Gods.
- A Corruption mechanic to ensures that spellcasters who meddle in demonology and other things that MAn Was Not Meant To Know suffer gradual degeneration of the type often seen in Gothic horror and dark fantasy.
- Expanded rules for crafting magic items, including some new rules for Alchemy. The new rules for enchantment from Age of Treason could be expanded with new options here.
- New rules for enchanted places that discuss common fantasy tropes such as places of power, haunted locations, ley lines, and places where temporary gateways to mythic realms such as faerie and hell spontaneously form.
- Rules for locations that enhance specific forms of magic, such as places that are aspected towards necromancy and areas that are aspected towards a specific element. This might also touch upon the concept of sanctified locations and the game effects of consecrated ground.
- Generic rules for planar travel, astral realms, and dreamscapes combat building on the existing rules from Elric.