GURPS - Magic

From their website:

"Within these pages, crackling with mystic energies, you'll find:

• The core magic system for GURPS, expanding on the material presented in the Basic Set . . . rules for learning magic, casting spells, enchanting magic items, and more!
• Complete alchemy rules . . . creating magical elixirs, using them, and even researching new ones . . . with an extensive list of known elixirs and their powers.
• Alternatives to the core magic system, including complete rules for improvised magic and rune magic. There are also guidelines for the GM who wants to change how magic works in particular worlds in a multi-world campaign.
• Plus special material from the GURPS Magic Items series and GURPS Wizards.

This is a powerful book, indeed. Use it wisely."