Path of Exile's four-month challenge leagues are a good testing ground for incremental improvements to items and game systems. A category of items that we're targeting in Sacrifice of the Vaal for improvement is Quivers. When playing in the new Ambush and Invasion challenge leagues, there are eight new Quiver base types that can drop, replacing the old series. The old ones still drop in Standard and Hardcore, but may stop spawning altogether when Ambush and Invasion end on July 5. There are several new Unique quivers planned that use the new base types, and it's possible that we'll port some or all of the old Unique quivers across to the new base types if they're here to stay.
Here’s the set of new quiver base types that can drop in Ambush and Invasion leagues: