I needed a rare Resourceful card, and this guy popped out. Originally I was thinking of making the card a 'double Nevinyrral's Disk, since I was looking for a powerful 'now and later' card that was unlikely to be activated two turns in a row. I didn't like how that card would be forced to not hit artifacts, though, and eventually came up with this, which seems more exciting to me. The cost and activation are set up so that you probably have to give a one turn warning... but if you have , feel free to just go for it.

Originally allowed you to swap any two player's creatures, which is what I'd prefer it to do. Unfortunately, it occured to me that the entire effect would fizzle if one creature died in response, since the card asked for an even exchange of creatures. I removed the targeting restriction on your own creatures so that you only had to lock in the number of creatures your opponent controls. Unfortunate... but better than having the entire card become undone by a Shock.