Bundle of Balloons. I replaced it with a Charm of Myths pretty quickly once I realized my wings were good enough anyway.
You can put another celestial stone in there. It stacks with the shell.Then my Celestial Stone which helped me a lot in 1.2 got easily replaced by the Celestial Shell. It may become my 3rd Permanent Accessory (4th in Corruption Worlds) By Permanent Accessory I mean an Accessory I use on every character no matter what I'm doing, no matter what class I am.
I actually still use these up into the Lunar Event-- they're extremely good against the Solar Pillar enemies if you have enough DPS boosts.fetid baghnakhs. The dps is awesome, but as enemy damage rises, the range is too short