The Ioun Stone of Mastery is a legendary item and so far as I know the only feature outside normal level progression that offers an increase in proficiency.

I would like to use one in my game but I am wondering about the power level. It looks to me like a combination of items that are otherwise much lower rarity, i.e. part of a Stone of Good Luck plus part of a +1 weapon plus a Wand of the War Mage.

Is that combination significantly better than the sum of its parts? Or is the legendary more due to a "coolness factor"?

In case this is relevant:

  • I never play tier 4, almost exclusively tiers 2 and 3.
  • I handle balance rather loosely.
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    \$\begingroup\$ Your 'sum of parts' doesn't include Spell Saves--might be more accurate to replace "Wand of the War Mage" with an Arcane Grimoire from Tasha's...but with the Class requirement stripped out. \$\endgroup\$ Commented Apr 3, 2023 at 12:36

1 Answer 1


You're missing a few things.

The Ioun Stone of Mastery provides a bonus to Proficiency which does more than you seem to think. It provides a bonus to...

  • Attack Rolls (Spell and Physical)
  • Saving Throws (that you're Proficient in)
  • Skill checks (that you're proficient in)
  • Your saving throw DCs (Spell save DC, as well as Racial and Class Feature DCs. Note: the only other way to magic item boost Racial/Class DCs is with items that increase your Attributes)
  • The usage limit on some abilities (for example: the updated Dragonborn from Fizban's can use their breath weapon a number of times equal to their Proficiency Bonus, reset on Long Rest)

And, most importantly, this stacks with everything for the cost of a single Attunement Slot.

If you have two +1 weapons, you don't get a +2 to your attack. There is nothing that gives you a bonus that the Ioun Stone of Mastery cannot stack with.

So, given the broad range of bonuses it offers, the fact that it consolidates multiple Attunement items down to a single Attunement slot, and the fact its bonus stacks with any other magic items you find....yes, I would agree that it deserves its Legendary rarity.

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    \$\begingroup\$ Several subclasses, especially more recent ones like in Tasha's, use your proficiency mod as a usage limit for some abilities, like Stars druid for multiple things (Cosmic Omen reactions to add weal or subtract woe, or to cast Guiding Bolt without a spell slot), and Peace Cleric. Also undead warlock Form of Dread uses, Pact of the Talisman uses. Also Hexblade's Curse damage. So yeah, lots of valuable things scale off this, and expertise in a skill double-dips it. Many racial abilities in newer publications of races (e.g. in MPMM) have proficiency uses per rest, too, like Firbolg invisibility. \$\endgroup\$ Commented Apr 4, 2023 at 3:39

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