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I was bored, so I decided to try to calculate what could be the highest total result one could obtain for a skill check.

Answers can include officially published material, including magic items - but no Unearthed Arcana. Wish is also not to be included.

NotArch
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Gael L
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    Are you allowing for variant rules to be used? For example, proficiency dice (which results in a 1d12 instead of a +6 for a high level proficiency) – David Coffron Apr 02 '19 at 14:45
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    Oh? I never heard of that before. I should check it out. – Gael L Apr 02 '19 at 15:13
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    @GaelL: It's an optional rule in the DMG (among other options for changes/replacements to proficiency bonuses). – V2Blast Apr 03 '19 at 01:13

2 Answers2

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The maximum result for a skill check is at least 169

The Rules

In order to maximize a skill check, we must use the following variant rules:

The Party

Our party, from Theros, consists of four characters:

  • A bard 15 -------------------------------------------------------- (for Bardic Inspiration)
  • A Circle of Dreams druid 6/ Wild Magic sorcerer 6 ---- (for pass without trace, Bend Luck, Hearth of Moonlight and Shadow)
  • An artificer 7/Peace domain cleric 1 ----------------------------------------------------- (for Flash of Genius and Emboldening Bond)
  • A hobgoblin Oracle rogue 1/ranger 10/The Fiend warlock 6/Any 3 ------- (for Oracle's Insight, Expertise, Save Face, Hide in Plain Sight, Dark One's Own Luck, Boon of Luck, and Boon of Undetectability)

Our friendly hobgoblin will be making a Dexterity (Stealth) check against a very perceptive foe.

The Gear

  • A luckstone
  • An Ioun Stone of mastery
  • The Lost Crown of Besilmer
  • 5 manuals of quickness of action
  • 5 tomes of clear thought (read by the artificer)
  • fresh mud, dirt, plants, soot, and other naturally occurring materials

The Calculation

  • Dexterity score is 30 (or a +10 modifier)
  • Flash of Genius adds 10 (Intelligence)
  • a Hero Point adds 1d6 (maximum 6)
  • Bardic Inspiration adds 1d12 (maximum 12)
  • Bend Luck adds 1d4 (maximum 4)
  • pass without trace adds 10
  • Emboldening Bond adds 1d4 (maximum 4)
  • Hearth of Moonlight and Shadow adds 5
  • Hide in Plain Sight adds 10
  • Expertise results in doubled 1d12 (maximum 24)
  • Dark One's Own Luck adds 1d10 (maximum 10)
  • Oracle's Insight adds 1d10 (maximum 10)
  • Save Face adds 5
  • Boon of Luck adds 1d10 (maximum 10)
  • Boon of Undetectability adds 10
  • luckstone adds 1
  • Ioun Stone of mastery adds 2 (thanks to expertise)
  • The Lost Crown of Besilmer adds 1d6 (maximum 6)
  • Roll a 20

Grand total: 169

Epic Boons of Fate

Finally, there is an epic boon called Boon of Fate which lets you add 1d10 to an ability check of any creature you can see. With enough creatures that have this epic boon you can make the total check immense. So basically, add 10 for each character with the Boon of Fate within 60 feet. Since you could use the Minimus Containment imprisonment spell to place them in extremely small spaces, there is effectively no limit to the amount of creatures you can fit in that 1.7 million cubic feet.

David Coffron
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    Step 16: How is hobby failing any check with a roll of 118? The highest DC given by the game is 30 which is labelled as "nearly impossible" – illustro Apr 02 '19 at 18:25
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    @illustro That's why I made it a contested check. Someone rolled 119 on Perception. Also, adventure modules have been known to have higher DCs – David Coffron Apr 02 '19 at 18:25
  • You should also include the chance of the character making that contested check rolling the maximum on all of their dice when working out the chance of a 123. – illustro Apr 02 '19 at 18:27
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    @illustro The chance is not calculable. That other character may have just used Divine Intervention, wish, or something to gain a ridiculous bonus on their next Perception check. It is not factored into my analysis – David Coffron Apr 02 '19 at 18:28
  • Presumably the skill check in question is Dexterity (Stealth)? At the point in time when the check is made, the Hobgoblin would be attempting to Hide - since it would have a Hide already in the triple digits, how are all the people with Epic Boons of Fate going to SEE it in order to use their Boons on its Hide attempt? – Kirt Aug 15 '22 at 20:26
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    @illustro From Rune Knight, but I now realize it is +2 to Strength and Constitution which Stealth is not. Updated – David Coffron Aug 16 '22 at 15:20
  • This answer could be improved by being more explicit about which character is doing the skill check, and what skill is being checked. – Joel Harmon Aug 16 '22 at 16:40
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    @JoelHarmon I originally had a lengthy section on that, but decided it was obtuse. I'll add just one line to show it. – David Coffron Aug 16 '22 at 16:44
  • A character with the Boon of Undetectability can't be targeted by divination magic and can therefore not be affected by guidance. – Joakim M. H. Aug 17 '22 at 13:42
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    @JoakimM.H. That's an obscure interaction. Good point; taken off – David Coffron Aug 17 '22 at 14:20
  • How does Expertise add doubled 1d12? I thought Expertise meant double proficiency bonus – stevenjackson121 Aug 23 '23 at 21:27
  • @stevenjackson121 The answer assumes the proficiency die rules (see the introduction) – David Coffron Aug 24 '23 at 12:33
-1

Arbitrarily Large

The Stealth skill has special rules that allow you to reuse the total for one check on the next so long as you aren't discovered1. Combined with the Epic Boon of Fate2 and the simulacrum spell3 this allows a character to simply achieve arbitrarily large Stealth skill checks with a sufficient investment4 of time. Banning Wish makes this also take an arbitrarily large amount of cash5, but that isn't a problem with the constraints in this question. No other skill does better than this6.

  1. "Until you are discovered or you stop hiding, [one's ongoing stealth check's] total is contested by the Wisdom (Perception) check of any creature that actively searches for signs of your presence.", PHB, C.f. https://rpg.stackexchange.com/a/110448

  2. This lets you add a bonus that stacks with all bonuses including from other Boons of Fate on account of Epic Boons not being Game Features for the purposes of the DMG errata changing some non-magical effects to no longer self-stack.

  3. Simulacrum lets you create copies of yourself you control. Despite putatively limiting you to one, in actuality that limit is very easy to bypass, and then you have arbitrarily many high-level wizard aides.

  4. That is, an arbitrarily large amount of time. Specifically, as check result increases linearly, time needed increases logarithmically.

  5. Because you are then casting via Glyph of Warding

  6. While parsimony demands similar treatment for checks made to disguise oneself or otherwise engage in a ongoing action contested by a variable series of shorter opposing actions, the rules only actually mandate check total re-use for Dexterity(Stealth) checks made to hide/sneak in particular.

V2Blast
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Please stop being evil
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  • Why is Stealth's 'special' property relevant? Can't you just build your army of simulacrums then they all use their Boon of Fate on you when you make any skill check? – BBeast Nov 20 '20 at 03:54
  • @BBeast almost, but not quite. I have not yet found a way for them all to be in range, even with readied actions, without the ability to build a check up over time. – Please stop being evil Nov 20 '20 at 20:46
  • @BBeast That is, with the XGE simultaneous action rule. With the PHB simultaneous action rule, you are correct, though the actual implementation necessary to get everyone in range at the same time with an infinite number of people is pretty technically complicated. – Please stop being evil Nov 20 '20 at 21:04
  • I don't think that special property of Stealth lets you build up Boon of Fates over time. The Boon of Fate can be applied when a creature you can see "makes an ability check". The special property of Stealth is not making the check repeatedly, but simply retaining the result of the check as the DC for future Perception checks. – BBeast Nov 20 '20 at 22:41
  • @BBeast is there a source for the future checks not being opposed? – Please stop being evil Nov 21 '20 at 00:11
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    I find nothing in the text to suggest that you keep "making a check" every round. In fact, it is to the contrary. It is an opposed check, but it appears to be an asynchronous check. You make the Stealth check once, and the result is persistent, but you don't repeatedly make the check with the same roll. That's how I read it, anyway. – BBeast Nov 21 '20 at 00:22
  • @BBeast you aren't making the check every round, you're making a check whenever it is called for. There's no provision for the sort of asynchronous checks you are talking about in the RAW. While they are a much better way of handling things than the written rules, the latter should be used for optimization questions. An opposed check is made by both parties, so you can add to either side – Please stop being evil Nov 22 '20 at 00:39
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    "When you try to hide, make a Stealth check. ... that check's total is contested by the Perception check of any creature that actively searches for signs of your presence." That sounds like you make the check once, when you hide, not every time someone searches for you. It's a contest, but it seems that this is precisely the RAW provision for the "asynchronous" check I talk about. – BBeast Nov 22 '20 at 01:08
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    I'll also point out that there is nothing in the Contests rules which say that the checks must be made at the same time. (Obviously, some situations require the checks to be made at the same time, but not all.) – BBeast Nov 22 '20 at 01:22
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    I think this discussion warrants its own question: Can you retroactively increase your Stealth roll while hiding? – BBeast Nov 22 '20 at 01:28
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    To use the Boons of Fate, you need to be able to see the person making the check - since they are specifically trying to Hide, wouldn't they eventually become so well Hidden that additional applications of the Boon would become impossible? – Kirt Aug 16 '22 at 16:34