This makes NO sense. To have a legal deck you must have 10 Basic Neopets in your deck, while you can only have 3 Neopets out in the Arenas. There are four arenas! Which means, unless you and your opponent both double up pets in the same two arenas that (with the exception of Villians) you and your opponent both get a free win per turn if you want. You can use this freebie for an equipment or Something Has Happened tap, but otherwise its a free bank or draw. Wizards did not think this through, and this makes it very easy to win. I've won over a hundred matches because I went first and played

Neopets in contests that my opponent wasn't strong in. They were playing Aishas, so I played my Myncis and Grarrls (AGI and STR) and they were too afraid to play anything except heroes in those arenas. I'm a little peaved about the come-and-gone aspect of the heroes, which limits their usefulness to getting rid of a villain or an gauranteed bank. A near-garuanteed bank is useful if your about to win, or If you need to get that book banked so you can draw that special card you need, or maybe just to get a draw, but with the exception of the few heroes with versatile special (out of battle) effects than they are very limited. However, Since many villains give a bonus to whomever defeated them after their defeat, it can be rather useful to play a villian and then use your own hero to destroy it, giving you a bonus and a bank/draw.