I've seen some hexagonal necklace item a few times that says it becomes awesome when you fuse it with erasers. No idea what it does though.
You can get erasers from the eggs, but I forget what they were used for.
Met a guy in-game and he said he got a scroll. Not those 100% ones
Different combinations of erasers plus the hexagonal thingy can net you a chair, Flaming Katana or Glowing Whip. And maybe some other items, but I only know those three.
This event is glitched, no way to open the etc exp egg. Richie won't open it no one is able to