Your beginning value is 1, so there are only four 'curios' to find:
One is found in the cave with the 'Spitter' enemies, after defeating their boss.
One is found in the Charger den, in the south-west part of the River.
One is found whilst rescuing the Hawkster Merchant's friend from the 'holding site'.
One is found in the 'dungeon' in the north-west area of the Stream.