Masters are special kind of magic user in Luminous Arc 2. They are chosen by Mother Lapis and given the ability to unite with Witches by absorbing their magical power through their Unity Ring, allowing the use of the corresponding Element, regardless of your own element (or in Rolands case if you ever used Magic at all). They are usually the heads of the Magic Association and thus need a high amount of knowledge about Magic and its history. On a side note, all masters get a familiar to their side, who serves either as a servant, pet or every other role the Master wishes, although Josie is the only familiar ever seen in the game. While it is confirmed that Masters existed over thousands of years, only two are known, said ones being Matthias and his son Roland. While usually it is impossible for two masters to exist, Roland is special, as his father had one half of Mother Lapis, while the other one gave Roland the powers of a Master as well.
After Roland becomes a Master, his stats get a good overall boost, with his magic gaining the highest, making him both a capable magic user as well as physical fighter, though he still excells in the latter. After uniting with a witch and reaching Level 30 with both Roland and the Witch in question, he gets access to the highly powerful sword spells of the corresponding Element. Said spells are Nocto, Ignis, Aero, Verdure, Aqua and Bright. It should be noted that, while being a master, Matthias never used any of the sword spells, but a lot of Shadow Frost Magic.