Glyphs are special books/scripts that enhance a certain unit greatly, along with changing the appearance at max level (usually 5). Glyphs can raise the critical hit rate, like for heavy onagers, increase succsess rate, like for Rock Warlocks, and more. Currently, glyphs are not available for every unit, but it is likely that more are in the works. Glyphs can be bought for gold (or possibly silver) on the Black Market. See "Force Upgrade" for more information on glyphs and their effects.The glyphs are upgraded with gold.