Ancient pages are items which are sometimes obtained when rummaging barbarian skeletons (1/13 chance) or as monster drops in the Ancient Cavern.
Rummaging skeletons gives a 1/13 chance of receiving an ancient page, while the spirits and skeletons have a 5/128 (1/25.6) chance of dropping them. In addition, mithril dragons have a 1/64 chance of dropping them. Brutal green dragons do not drop the pages.
A good strategy on claiming ancient pages is to rummage the three skeletons found on the lower level, and hop to another world.
Monster Combat level Quantity Rarity Mithril dragon 304 1 Skeleton hero 149 1 Skeleton brute 126 1 Angry barbarian spirit 152 1 Berserk barbarian spirit 152 1 Enraged barbarian spirit 152 1 Ferocious barbarian spirit 152 1 Skeleton heavy 132 1 Skeleton thug 122 1 Skeleton warlord 130 1