[RPG] Can you milk an Ivory Goat

Creating custom items is always a matter of negotiation and judgment; there are no hard and fast rules. The books provide some guidelines, but are always quick to point out that they cannot be relied upon, and that the DM is always going to have to judge suggested custom items on a case-by-case basis.

The first guideline is to compare your desired item against the closest available comparable items, and adjust from there. Thus, to allow a ring, such as Devlin’s, to do what the quiver of Anariel does, you would start with the quiver of Anariel as your basis for the cost of doing so.

Furthermore, the passage on page 233 of Magic Item Compendium is really talking about adding new magical abilities onto an item that could otherwise have that ability. But ultimately, you can add anything anywhere as long as the DM allows it. The aforementioned guidelines suggest a 50% surcharge to add something to an unusual slot. So to put the quiver of Anariel effect on a ring should, by these guidelines, cost 50% more. On the other hand, the guidelines also suggest that something that does not use one of the usual magic item slots should cost double, so a magic quiver (which doesn’t prevent the use of other items) presumably costs double. So the guidelines would say that the ring should cost approximately 75% of what the corresponding quiver costs.

However, the problem here is that the quiver of Anariel is ludicrously overpriced, particularly at the regular arrows level. My games routinely ignore tracking mundane arrows in general, so they are literally charging 28,000 gp for a magic quiver that does what any quiver in my games does, by default.

On the other hand, magic arrows are a much bigger deal than mundane ones. Magic arrows partially stack with the magic properties on the bow shooting them, which is a big deal. While I’d say even Devlin’s ring is on the expensive side for mundane arrows, for magic arrows the cost definitely should be much higher.

So instead, I’m going to make a different suggestion: consider magic ammunition as if it were a 50-charge item, like wand. After all, enhancing 50 arrows costs the same as a sword. So if a 50-charge spell-effect item costs spell level × caster level × 750 gp, and a use-activated at-will item costs spell level × caster level × 2,000 gp, you’re looking at the use-activated version costing 2⅔× what the 50-charge version does. So if you apply a 2⅔× multiplier to the cost of 50 magic arrows (which is the same as the cost of a single magic sword), you have at least one reasonable idea for what this effect should cost.

The results are 5334 gp for +1, 21,334 gp for +2, 48,000 gp for +3, 85,334 gp for +4, and 133,334 gp for +5. Most likely you would ideally use equivalent levels of special weapon properties rather than straight enhancement bonuses, though.

It should be fine, as long as time allows.

Nothing in the rules says that a long rest cannot immediately follow a short rest. In this case, what the characters are doing during those rests are very different.

Indeed, a short rest and a long rest are what many real-life people do before bed: an hour or so of non-strenuous activity, like reading, and then going to sleep. It's not a stretch to say that a D&D character can't spend an hour studying their magical item, and then go to sleep.

The only time where that might be a problem is if the characters don't have the full 9 hours.

Different things are happening during the two rests.

What's really key here is that the activities during the two rests are different. In the short rest portion, the character is studying the magic item, meditating on it, or whatever is required for attunement. In the long rest portion, the character is doing something else, such as sleeping. The attunement process is still active work, just not active relative to adventuring.

I think that this distinction is why attunement is limited to short rests, and why a character should be able to do chain them together.