A small, mundane-looking pouch made of leather and linen. On closer inspection, one can notice that the linen is interwoven to represent specific sylvan symbols that radiate minor magic. It is a legendary accessory of the most distinguished fey and elven heroes, who used these pouches to outmatch their opponents. Even though only a rare few druids know the technique of creating these, those created long ago still persist in the world, often hidden in hoards of dangerous creatures or lost in the wilderness, resting with their previous users until a new hero finds them again.

Enchanted Pouch: The pouch has the ability to imbue bullets placed inside it with 2 Arcane Options available to the Arcane Archer subclass from Fighter(randomly determined or chosen by the DM upon being found). The save DC against these Arcane options equals 8 + your proficiency bonus + your Intelligence modifier. These options grow in power when you become 18th level character as if you were a Arcane Archer of the same level.
The pouch can contain up to 10 bullets. For purposes of this item, anything that can be used as ammunition for a sling is considered a bullet. When you finish a long rest, a number of bullets inside the pouch equal to your Intelligence modifier become enchanted with one of Arcane Options available to it(your choice of which). Additionally, if the bullet was not already magical, it becomes magical for the purposes of overcoming resistance to damage from non-magical weapons.
When you use one of these bullets, they immediately use their Arcane Option. After the attack hits or misses, it loses the enchantment it gained from this item, this also happens if the bullet spends 8 or more hours outside the pouch.

Sylvan Trickery: You can simultaneously attune to any number of Sylvan Bullet Pouches that is lower than your proficiency bonus. When you attune to a Sylvan Bullet Pouch beyond the first, they permanently combine into a single item and its rarity increases by one.
The new pouch gains the Arcane Options of the newly attuned pouch, and its total capacity increases by 10. However, the number of bullets that can be enchanted per long rest stays the same.