We were going to allow people to reset challenges via BuyCraft but instead decided to offer it in game.
Let's get a whole new market going and see where it takes us.
Netherstars may be useful for other things as well stay tuned!

Use /warp shop in SkyBlock to buy/sell netherstars with/for EXP.
Use your challenges menu via /c to reset your challenges with 200 netherstars.