Treasure chest odds courtesy of DGDobrev:
http://forum.1cpublishing.eu/showthread.php?t=11640
About every 11.5 battles you'll get at least one playing randomly. So to play a complete 300-battle game, expect to
actually play about 3500 battles.
About once every 37,000 battles (on average) you'll dig up three wanderer's scrolls in one battle. If you did everything to fight as many battles as possible, you might manage 320 battles in one game. So the upper limit on wanderer's scrolls is around 960 from your pet dragon. Add in 15 from Elenhel, and maybe 25 from the world map, and you've got about 1000 wanderer's scrolls total.