How is the power of a magic item measured according to the rules?

Premise

The DMG states a relation to a magic item's power, it's rarity, and character level.

Rarity provides a rough measure of an item's power relative to other magic items. Each rarity corresponds to character level..

It follows up immediately with an example

A character doesn't typically find a rare magic item, for example, until around 5th level.

Question

The rules seem to have some sort of definition of what power means. What is it?

Rationale

A number of questions seem predicated on estimating the power of a magic item. E.g:

• I'm not sure that this is POB. It seems to me that the rules are using a word and it is fair to ask what the rules mean by that word. Even if the answer is: "the rules don't specify" it seems like this question is still very much answerable. I don't see where the opinion comes in as long as we stick to our answering guidelines as usual. – Rubiksmoose Nov 30 '18 at 16:56
• In addition, having an answer (or non-answer) to this greatly impacts many other questions here and we approach them. – NautArch Nov 30 '18 at 18:16

On DMG p. 285, in the "Power Level" portion of the "Creating a Magic Item" section, there is a brief discussion of how two measurable levels of power (spell level and static bonus) relate to rarity.

That brief section includes this table:

Magic Item Power by Rarity

$$\\begin{array}{|l|c|c|} \hline \textbf{Rarity} & \textbf{Max Spell Level} & \textbf{Max Bonus} \\ \hline \text{Common} & \text{1st} & \text{—} \\ \text{Uncommon} & \text{3rd} & \text{+1} \\ \text{Rare} & \text{6th} & \text{+2} \\ \text{Very Rare} & \text{8th} & \text{+3} \\ \text{Legendary} & \text{9th} & \text{+4} \\ \hline \end{array} \$$

But beyond this table there isn't really any other concrete discussion of power level being linked to rarity.

There is also a brief discussion about attunement, but nothing much beyond how it should be used as a tool to prevent abuse. This implies that lack of attunement increases an items power level.

The discussion in the DMG is however combat focused, and as such doesn't consider the social or exploratory pillars of the game.

• Additionally the section I mentioned on attunement in the DMG is specifically about putting a limit on the item to prevent it being "passed around" the party to gain a lasting benefit, or to limit the number of items that can be stacked together. Those limitations are a clear way to reduce an items power. As such an item without attunement doesn't have this limitation is clearly more powerful. Take the ring of free action. If you remove the attunement then suddenly hold person doesn't work on any of your party (as the ring can just be passed from character to character as needed during combat) – illustro Dec 1 '18 at 1:07

It's not clear

The rules do not clarify exactly how "Power" is measured relatively. They also do not seem to provide a methodology that can be used to look at the known examples of items and figure out what was used to determine their "power rating".

Without either an explicit or implicit mechanic for measuring "Power", it is left as an unknown. That's not helpful for us as community in trying to figure out how to measure a homebrew item or a change in an existing item, but it does seem to be the reality of the situation.

Until we have a clear methodology, we are left making the judgement calls ourselves based on our players, our worlds, and our tables.

• Usually we compare it to other magic item. Does that count as methodology? – Vylix Dec 1 '18 at 0:09
• @vyliz No, a methodology is how you do the comparison and that's what we don't have. – NautArch Dec 1 '18 at 0:12
• The shear breadth of abilities a magic item can have is the biggest problem, in many cases comparing two magic items is like comparing apples and cadillacs. – John Dec 1 '18 at 6:57
• Comparing items to items doesn't work either. Compare broom of flying (uncommon, item fly all day, no attunement) to wings of flying (rare item, 1 hour max, attunement). Short answer - it's a mess. – Greenstone Walker Sep 10 '19 at 22:58

Regarding the "Magic Item Power by Rarity" table (DMG, p. 285) referenced in illustro's answer, I have found that magic items add rarity to increase their frequency of use or range of effects. So, a good set of rules of thumb are:

1. Once per day is the base rarity
2. A charged item regains d3-d6 +1 charges per day at a cost of one rarity higher than the spell that created it
3. An 'at-will', or continuous effect, item produces a magic item that is two rarity levels higher than its originating spell
4. If the spell requires Concentration, then the magic item typically requires attunement
5. If it has multiple effects then increase the rarity by at least one more level, unless it has a self-destruct mechanism, like several Staffs with multiple spells.

For example:

• A charged wand of Magic Missile (L1) is Uncommon
• A charged wand of Polymorph (L4) is Very Rare and requires attunement
• An 'at-will' Ring of Featherfall (L1) is Rare and requires attunement
• A charged Staff of Frost has multiple spells, with Wall of Ice (L6) as it's highest level spell, but can be destroyed by overuse, so it's Very Rare.

Finally, if the result is overpowered then the rarity is probably one higher, e.g. Ring of Invisibility (L2) is Legendary, not Very Rare. And if it only gives a bonus to a single ability check, or other limited effect, then it's probably one rarity lower, as with the 'at-will' Ring of Jumping (L1), which is only Uncommon, not Rare as we might otherwise expect.

Obviously, this method isn't perfect or complete, but I do find it to be a useful heuristic for building custom magic items. Hopefully that helps!

• Hi Adrynian, welcome to rpg.se! Take the tour and visit the help center for more information. This is a pretty good first answer. Did you determine these rules by analyzing the existing items and trying to create your own with the given rules? If you are any additional rules source or reference you used to work these out you should add it to the answer too. Good job, thanks for participating and happy gaming! – linksassin Sep 10 '19 at 5:42

It could also be tied to the "level" of the adventurers. A farmer that picked up a sword to fight to local riff raff (level 0 / Commoner) probably isn't rocking a +3 longsword. But, a seasoned Dungeoneer who has taken down all manner of beasts, beholders, and beguiled is more likely to find that sort of thing in their time out and about. As the overall status / level / power of the PC increases so does their likely rewards or found loot.

This idea is in the DMG and the PHB

• Can you cite the specific pages in the DMG and PHB that support this? – NautArch Nov 30 '18 at 20:50
• Welcome to RPG.SE. Please support your point with references from the DMG and PHB: you pointed to it, but you need to follow through to support your answer. As this isn't an internet forum (see the tour) the standard for an answer that remains open, or attracts up votes, is a bit higher in this format. Take a look at what illustro did in that answer. – KorvinStarmast Dec 1 '18 at 1:43