Items that can be exchanged for the eggs
between level 30 and level 52:
red potion, blue potion, green potion, purple potion, peachblossom, kaki blossom, gango root, bellflower, Tue mushroom, Alp rose, Lilac, mulberry
with 20 eggs: skillbook, quartz sand, fingerbones, magic seeds
between level 52 and level 74:
red potion, blue potion, green potion, purple potion, peachblossom, kaki blossom, gango root, bellflower, Tue mushroom, Alp rose, Lilac, mulberry
with 20 eggs: skillbook, water crystal, blue crystal, silver arrow
level 74+:
green potion, purple potion, goldgish sushi, carp sushi, salmon sushi, catfish sushi, silver arrow
with 20 eggs: skillbook, book of riding, demons ashes, icemarble+ quartz sand, magic seeds, water crystal, blue crystal
note: for the items with 20 eggs: you have a chance to get these items! you don't get one of these items 100%!
also, the amount of items you get is variable, you can get for example 37 catfish sushi when you trade 20 eggs .