"I'm sorry. I was just wanting to make sure that I am reading this properly. Is the mageblade in Unearthed Arcana? I have been looking for it, but seem unable to find it. Thanks."
Sorry PenKnight, but no, you've got it confused. The Mageblade appears in Monte Cook's Arcana Unearthed, which was cleverly named after the same old-skool supplement that the 3.5 Unearthed Arcana was. AU is a fully playable d20 system with it's own classes (such as the Mageblade), races, feats, and magic system that all fits together in the "implied setting" of the Diamond Throne Empire, whereas UA, as you are probably aware, is a toolbox of options for 3.5 D&D.
Monte has since released a deluxe, "director's cut" edition of AU, which he re-titled Arcana Evolved to avoid this sort of confusion.
Robert "Will Save vs. Confusion" Ranting