The movie reveals that the name Dororo means "Little Monster", but doesn't mention that the name of the sword and character - Hyakkimaru - means "Hundred Demons."
In order, the monsters that Hyakkimaru fights are: Jorogumo (spider demon), Maimai'Onba and her Hanyo (moth and caterpillar demons), Ki Oni (cherry blossom tree demon), Tokage Oni (lizard demon), Daitengu (bird demon), Inu Oni (dog demons) and Ratto Oni (rat demon).
Some of the demons Hyakkimaru fights are based on traditional Japanese creatures. The spider demon is a Jorogumo and the winged male demon is a Daitengu. The other demons are unique creations to the Dororo brand or just labeled as various generic Oni.
The stringed instrument that Bipa carries is a short-necked Japanese lute called a biwa.