it can be spawned from a random chest(not a dug up chest by a dragon IIRC)

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.

so according to DGDobrev:

Chests dug up by the dragon give:

- Gold (72%)
- Random scroll (15%)
- Crystals (5%)
- 1 random rune (5%)
- 1 wanderers' scroll (3%)

the chance of not having a crystal/rune/wanderer scroll would be 87% per chest, which means if i want to make sure that i get at least one of crystal/rune/wanderer scroll for a battle, there is a 71% chance that i can get it within 3 tries (3 chests per try, so 9 chests in total), or 88% within 5 tries(15 chests)...or 95% within 7 tries(21 chests)!!! this is pretty exciting news!