The Longbow of Diana should create arrows on-the-fly as a passive effect when it is fired, rather than creating a stock of +0 arrows as an invoke ability. The arrows could be ordinary arrows with an enchantment equal to the Longbow’s, but it’s probably more interesting to clone arrows from your quiver (assuming the thing you have quivered is suitable to be fired from a bow), as this lets you keep multishot bonuses from using same-race ammo or use silver arrows and preserves the incentive to have well-enchanted ammo. Cloned arrows should always be destroyed when they hit the ground, so you can’t use it to create hundreds of highly-enchanted arrows.

A slightly different way to take this idea would be that arrows don’t get created on the fly, but automatically return to your quiver when they hit the floor. This means that any arrows that get eroded by hitting a rust monster or something will return to you eroded, and any arrows that get mulched will still be lost, preserving the ammo management aspect of the ranged combat game. On the other hand, it could be argued that removing ammo management for the player is a great benefit for a quest artifact to have.

The Longbow of Diana should put a floor on the amount of multishot arrows fired from it, so you always get a good multishot. The floor should maybe even just be set to the maximum possible multishot you can achieve.

The Longbow of Diana should be usable for firing arrows without actually wielding it, but this reduces the amount of multishot you can get out of it. This could be flavored as the bow hovering on its own and magically pulling the arrows from your quiver. The main motivation for this is to bring the Longbow to parity with throwing darts, which require no launcher.

The Longbow of Diana should still provide reflection when it is in the offhand slot and not actively wielded.

Make the Longbow of Diana able to change shape between the different types of launchers (bow, crossbow, sling), either by invoking it or simply by applying it. This allows Rangers to play with whatever type of ranged combat style they prefer, and allows gnomish Rangers to use a crossbow without being coerced into switching to bow later.

All arrows created by the Longbow of Diana come pre-identified so you can readily see their enchantment.

Invoking the Longbow of Diana gives you light arrows. These are a special object, weightless, created with the same enchantment as the Longbow, but attempting to enchant them further will fail (maybe making the enchanted arrows evaporate). If they leave your inventory for any reason, they will vanish. As a weapon, they are very powerful (to the point of probably instakilling most weaker monsters they hit). To prevent the player stockpiling them, the invoke effect will only top up the amount of them in your inventory to 5.

When a light arrow strikes a target or falls to the ground (and vanishes in the process), it permanently lights up the surrounding area.

The arrows created by the Longbow of Diana are of your race/role’s affiliation (e.g. orcish arrows for orcs, ya for Samurai, etc), and bear the same enchantment as the bow itself.

Invoking the Longbow of Diana gives a temporary buff of “piercing”, in which all your projectiles (not only those fired from the bow) pierce through monsters and continue flying.

Arrows fired from The Longbow of Diana will never break and will automatically return to you. It also counts as your racial bow regardless of your race.

The Longbow of Diana has different effects based on which alignment you are (or perhaps it’s just different artifact bows, only one of which appears). Lawfuls get an Apollonian bow which shoots gold arrows which have higher base damage. Neutrals’ bow fires silver regular arrows. Chaotics’ bow automatically poisons fired arrows.

Yumis should be treated as “very well-crafted bows”, and they should allow elf or orc multishot to be used with them (as opposed to the current where you need to use an elvish/orcish bow). The Longbow of Diana’s base item should be changed to a yumi.

If you are a gnomish Ranger, the quest artifact should be a crossbow.