The beastmaster crown is pretty hard to acquire without a good sense of mathematics. It is in Invidia. Go to the girl who offers the math mini-game, and play the game. If you score over 250 points, she will commend you and the crystal will bestow the Beastmaster crown upon you. To earn above 250 points is quite hard. Scoring big points (in general) can be easy when you use this example to the best of you abilities:
Say you have the numbers: 3, 7, 9, and 9. Add the 3 and 7 to make 10 prematurely, then multiply the 10 by 9, subsequently dividing by 9 to once again get a total of 10. Doing this will use all four numbers given, and will give you a nice 110 points (based on the totals in the longer equation - in this case: 10, 90, and 10). Any combination where you can make 10 before using the twinned high numbers works great. since 250 divided by 3 is 83 and a third, you would need at least 84 points (averaged over the full three rounds) per round to get the crown.