You'll find the Lamia Harp, a nice upgrade for Edward, in the southern room. Moving north down the path, you'll see stairs to the save point on the first floor. There is also some Treasure to collect there.
After returning, collect the two chests along the north wall, then head for the stairs to the south to reach the Antlion's nest.
After returning, collect the two chests along the north wall, then head for the stairs to the south to reach the Antlion's nest.