Equivalent Exchange is the major magic mod that's included in the Technic Pack. This mod covers everything from magical dusts to repair tools and armor to talismans, rings, and generators to duplicate items. One of the main items is the philosphers stone which is made with a diamond, four glowstone dust, and four redstone, and is used for making several types of magic coal, making the higher-tier transmutaion items, and changing blocks in the landscape.
Once you gain more dusts and other ingredients you can create rings that allow you to fly, tables that let you trade items and collecters that convert sun into EMC, EMC is the fuel of Equivalent Exchange it lets you trade items for it or create other items from it, it will also "fuel" any magical items that you have created.
On some servers Equivalent Exchange is disabled because it is considerd "cheating" because it allows you to spawn items and fly around which some people dislike.