The alpha stigma gives the user the ability to analyze and copy any magic they see used, even only partially completed spells as demonstrated by Ryner when fighting the spies from Gastark. It is even shown that not only can Ryner copy magic but it seems he empowers it as well as seen in episode 1 and in the light novel he can overpower dozens of other mages while using the same spell as they are.
Master Yen Sid is a master of the magical arts, able to perform powerful magic spells comparable to Merlin's. He has shown the ability to teleport, create illusions while training Mickey, and create cosmic smoke to locate a person. He seeks counsel with the stars to predict the conditions of the present and the future, which allows him to gather information about the worlds' condition and to pass it on to his allies. He can summon objects of his with a simple hand motion. Yen Sid is also extraordinarily powerful in the use of light, as he was able to part an immense amount of Heartless long enough for the Guardians to proceed. 781b155fdc