Limits (or lack there of) on UMD

[Buufreak]

From another thread:
One core rules example of UMD is a Rogue emulating Turn Undead to gain a virtual Turn Undead attempt which gets channeled into an item.



Following this, could a cleric that is out of turn attempts for the day use UMD to fool an item to think they aren't?

[Biffoniacus_Furiou]

That's a very liberal interpretation of UMD. Let's take a look at where that's coming from:


Emulate a Class Feature
Sometimes you need to use a class feature to activate a magic item. In this case, your effective level in the emulated class equals your Use Magic Device check result minus 20. This skill does not let you actually use the class feature of another class. It just lets you activate items as if you had that class feature. If the class whose feature you are emulating has an alignment requirement, you must meet it, either honestly or by emulating an appropriate alignment with a separate Use Magic Device check (see above).

Let's say ye olde Rogue with UMD has an Arcane Thieves' Tools from MIC, and wants to UMD their swift-action activation:


When activating the tools, you can expend
an arcane spell or arcane spell slot of 1st
level or higher to gain a +5 competence
bonus on either a Disable Device check
or an Open Lock check begun before the
end of that turn.

UMD lets you pretend you have arcane spell slots, but it doesn't grant you any spell slots to spend per the bolded portion above.

The same goes for Turn Undead, it lets you pretend you can do it, but it doesn't grant you uses of the ability to spend on activating items.

[Troacctid]

In my opinion, the item "knows" how many times it's been activated, and once you hit the limit for how many times a character of the imitated level would be able to activate it, you can no longer get more uses out of it.

For example, if you have a shield of vigor, which require a use of the knight's challenge ability, you could use it once with a DC 21 check to imitate a 1st-level knight, but since a 1st-level knight only has one knight's challenge per day, the second use would require a DC 22 to imitate a 2nd-level knight. Then the third use would be DC 23, and so on.

[Nifft]

UMD lets you pretend you have arcane spell slots, but it doesn't grant you any spell slots to spend per the bolded portion above.

The same goes for Turn Undead, it lets you pretend you can do it, but it doesn't grant you uses of the ability to spend on activating items.

Here's what the PHB says, with a highlight where it starts to consider this case:

https://i.imgur.com/YMAYQ9o.png

So per the PHB, you can activate the item, but you can't otherwise use the ability.

UMD doesn't give you spells or spell slots, but you can trick the item into thinking you have and expend a slot by rolling UMD, just like Lidda tricked the chalice into thinking she'd expended a Turn Undead attempt.

-- === --

The obvious and fun application is a Runestaff from MIC.

[NigelWalmsley]

I believe Knowstones are also templated in a way that lets you abuse them with this.


Following this, could a cleric that is out of turn attempts for the day use UMD to fool an item to think they aren't?

Yes, but they would have to roll high enough to emulate the class feature, at which point they're probably better off just doing that in the first place.

[Silva Stormrage]

In my opinion, the item "knows" how many times it's been activated, and once you hit the limit for how many times a character of the imitated level would be able to activate it, you can no longer get more uses out of it.

For example, if you have a shield of vigor, which require a use of the knight's challenge ability, you could use it once with a DC 21 check to imitate a 1st-level knight, but since a 1st-level knight only has one knight's challenge per day, the second use would require a DC 22 to imitate a 2nd-level knight. Then the third use would be DC 23, and so on.

This is how I generally handle this clause with UMD as well.

Though for Runestaves and such I generally don't allow you to actually cast the spell. The Runestaff gives you access to the spell if it's on your class list. So a successful UMD check would let a cleric use a wizard spell but a rogue using a runestaff would effectively have the runestaff's spell added to the rogue's "Spell List" which is non existent. But since the rogue doesn't have a spell slot they know the spell but can't cast it. I am not 100% sure on the RAW of that but it does seem to fit RAI.

[Zanos]

It's often a popular interpretation of UMD that you can't use it to activate items that consume a class feature. The given example in the book with UMD pretty clearly disagrees with that popular interpretation. I would say as long as consumption of the class feature is listed as a cost of activating the magic item and not phrased as 'when you do x class feature you can activate y magic', then you should be able to UMD it.

So a cleric who is out of Turn Undead attempts should be able to UMD an item that requires them to expend one.

[Buufreak]

Now, screwball question: say a rogue with cha 16 does this exact setup, as quoted directly from the book. He has now emulated a cleric of 1st level and their ability to turn undead. At 1st, cleric can turn 3 + cha mod times per day. Has the rogue enabled 6 uses of this item with the single skill check?

[Nifft]

Over in another thread @Troacctid pointed out that Runestaves have an attunement requirement prior to use -- which isn't activation, but which seems to rely on a class feature.

One of the following cases ought to apply:

1 - You can't attune a Runestaff, so you can't use UMD to activate it (and use UMD to replace expending a spell slot).

2 - You can use UMD to activate a Runestaff without attuning it by pretending you attuned it as a separate UMD check before you make the UMD check to activate it. This would be similar to how you might also need to make a third UMD check to emulate having an Intelligence or Charisma score high enough to cast the specific spell, just like you might need to do with a scroll.

3 - You can use UMD to attune a Runestaff by spending an hour each morning pretending to prepare spells. According to the Rules Compendium, to keep up ongoing fakery of other types (alignment, race, etc.) you need to make an upkeep UMD check every hour, so maybe you need to keep rolling to fake that you have spells. Then you'd just need a single UMD check per activation to fake expending a spell-slot.


It's my opinion that either (2) or (3) is reasonable, but I honestly can't decide between them.