About in the middle - her significance is she is 'protected' from all colors and she pretty much attacks the player directly. Think of it this way - you start out with 20 'life' and your goal is to take your opponent down to 0 'life', so you play just like a card game - you each take 'turns'. You have to get enough 'mana' cards down to play one of your creature cards and you can only put one 'mana' down each time you have a turn (that's supposing you have any mana cards in your hand - 7 cards each player to start). No matter what kind of creature card the other player has on the table - the Angel can fly right through their defenses to attack them personally. So in a simple game, unless they can come up with something to 'kill' the Angell or defend themselves - it would only take 5 hands (or less if they're already damaged) after the Angel came out to 'kill' your opponent. That's why it's so expensive to bring her out. Some cards are cheap (cost less mana to bring out) and thus can do some damage to the other player early in the game. This is keeping the strategy simple and I'm sure there is some defense against her - I just haven't looked at the newer cards. <img src="/ubbthreads/images/graemlins/disagree.gif" alt="" />
You're right it's really expensive to try and stay up with all the cards. <img src="/ubbthreads/images/graemlins/disagree.gif" alt="" />