The Cat Claw found in the middle chest is a nice upgrade for Yang, but if you brought an Ice Claw, you'll want to keep using that (though two is overkill). The southeast stairs lead to an area of the 4F containing the Archer Bow and a Notus. Work your way north and around to find the stairs that continue through the dungeon. You'll start to see Eggs on this floor. These enemies are just normal enemies in disguise, but they won't Hatch until you hit them. Make that hit count, and sometimes you can win the fight before it starts.