The upper right of each magic card always tells you how much mana you need. Magic divides mana into Plains (*), Fire (red), Water (Blue), & Black - I also think there's a nuetral (I haven't played in awhile, so my memories a little fuzzy). You can't put a card into 'play' if you don't have enough mana (also the correct type) out on the table to play that a character card.
As BG said, the 5 means 5 of any kind of mana, the '*' means one Plains and the blue 'drop' means one Water. She's pretty expensive, but she can attack and no one can defend against her - so she damages the player themselves (you only start out with 20 life). So if I have the angel and I attack you, you lose 4 life unless you can some how foil my attack. <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" /> If I get your life down to zero - you lose. <img src="/ubbthreads/images/graemlins/badsmile2.gif" alt="" />
