A toad egg sac is an item that is gained from harvesting reeds. When opened, it places 15 swamp toads in the player's inventory. You must have 15 empty inventory spaces open, or you will not be able to open the egg sac. Players also may receive swamp tar and swamp lizards from harvesting reeds, but they are not obtained by opening these; rather, they are separate yields.
After a hidden update on 14 April2014, the egg sac now has a "Open-Noted" option which allows you to withdraw the contents in noted form.