Phantom Blade Zero has two distinct weapon types: Standard Weapons and Phantom Edges. The latter are heavy-hitting weapons with limited charges, but also double as traversal and exploration tools that can unlock new areas and help you get your hands on hard-to-reach items.
A lot of these are optional in terms of core progression, and one such easily missed Phantom Edge is the Feather Bow, an early-game option for getting hanging items down from high places. To get this, you'll need to complete the quest 'Purge The Sect', and this is how to go about it.
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How To Begin Purge The Sect

To begin this quest, you'll want to head to the Outpost Bell. In this camp you'll find a man on a roof that you'll be able to climb up to and talk with. If you do, you exhaust their dialogue options.
This will start the quest and mark the area where you can kill the Sect and get the Feather Bow.
Purge The Sect Bow Location

To get to the area where you fight a mob of enemies, you'll need to defeat Peng Meng, the Axemaster. This is a reasonably easy early game fight, and defeating them will grant you the Dread Axe, which will open up the path ahead.

You'll then want to head to the area shown on the map. Here, you'll find a variety of mob enemies, some with ranged attacks, and some who are more melee-inclined. Focus on taking out the ranged attackers first, and then turn your attention to the melee enemies before you get swarmed.
Tip: Using the rightmost ladder, you can aerial assassinate and stealth attack the ranged enemies without triggering combat.
After defeating them, you'll immediately be rewarded with a Blackstone Fragment and the Broken-String Bow. Plus, you'll also be able to open a nearby chest that will contain the Token of Pursuit accessory. You can then take the Broken-String Bow back to the NPC at the Outpost, and they will fix it up for you, completing the quest.
Using Your Bow & Alternative Options

As mentioned, this Phantom Edge has a dual use. You can use this as a means of taking potshots at enemies from range, although the limited charges make this a lot less attractive a prospect than the Dread Axe early on.
The good news is that you don't need to have this Phantom Edge equipped at all to use its secondary function. This bow can be used to shoot down hanging items around the map, and the prompt will pop up on screen if you're in range.
We also feel that it's good to mention that this is not the only early-game ranged Phantom Edge you can earn. You can also gain the Flying Dagger from Quick Hand Zhang if you find all of the treasures in the Crimson Forest region.
That said, Purge the Sect is a very easy quest to turn in, so loop back to the Outpost when you get a chance and add this to your Phantom Blade collection.