The main player-to-player trading currencies are Glim and Flux, but just about anything can be offered up, such as Chaos Chests. Flux is a very common type of trading currency by players. This item is not an official currency, but many use it for trading the vast majority of the items in the game. 

 An abundant amount of players use this as a currency for these reasons:

·Flux is a tangible in-game item that can be traded among players and most marketplace sales are conducted with flux.

·Flux can be used to craft/ buy the other market currency, Penta-Forged Shadow Souls.

·Having flux as a main trading material can allow players to get nearly every item in the game without paying any money

·Flux is also stored in your crafting inventory, Megaflux Tanks are no longer needed for storage.