Free tables Natural 20 — skill checks

Natural 20 Table — Arcana Skill Checks, d20

A free d20 table for a natural 20 on a Arcana check in 5e. Twenty outcomes, from solid to legendary.

A natural 20 on a skill check is not a critical success in fifth edition — criticals apply to attack rolls only, and a 20 on a check is simply a 20. Which is why a legendary roll so often feels like nothing happened. This table gives it somewhere to land.

Twenty results written for Arcana specifically. A legendary Arcana roll has nothing in common with a legendary roll at anything else, which is why there are eighteen of these and not one.

Roll d20 when a player rolls a natural 20 on a skill check and succeeding quietly would be a waste.

Severity tiers

Each result names its tier, so you can see at a glance how bad a roll was without decoding a colour.

Solid 1–10 — Cleanly done, with something small to show for it.
Impressive 11–17 — Better than anyone expected. Momentum, or an obstacle gone.
Legendary 18–20 — Scene-shaping. The kind of success people repeat afterwards.

The table

20 results. Roll d20.

d20	Result	Tier	What happens
1	Named It	Solid	You identify the effect precisely — school, rough level, and what it's doing. No extra effect.
2	Found the Seam	Solid	You spot where the magic is weakest. Anyone attempting to dispel or disrupt it has advantage.
3	Read the Hand	Solid	You recognise the caster's style or tradition, and could identify their work again anywhere.
4	Safe Distance	Solid	You know exactly how far the effect reaches, and can tell the party where to stand.
5	Counted the Charges	Solid	You learn how much use the item, ward, or effect has left in it.
6	Harmless After All	Solid	You establish with certainty that one thing the party was worried about is not dangerous.
7	Quick Study	Solid	You have advantage on your next Arcana check this scene.
8	Spotted the Trigger	Solid	You learn what sets the effect off — and therefore how to avoid setting it off.
9	Explained It Well	Solid	One ally who listens gains advantage on their next saving throw against this effect.
10	Recognised the Component	Solid	You identify a material component or reagent here, and it is worth taking.
11	Found the Off Switch	Impressive	You work out how to end the effect without dispelling it. It takes an action and no roll.
12	Turned It	Impressive	You can redirect the effect's target or area once, as an action, before it ends.
13	Full Schematic	Impressive	You understand the whole working — what it does, what it cost, and what it was built to protect.
14	Attuned Faster	Impressive	If this is an item requiring attunement, you attune to it immediately with no rest required.
15	Warded the Party	Impressive	Every ally who can hear you has advantage on their first saving throw against this effect.
16	Traced It Home	Impressive	You learn where the magic came from — the caster's location, the source, or the binding site.
17	Copied the Method	Impressive	You can reproduce a limited version of this working yourself later, given time and materials the DM specifies.
18	Unmade It	Legendary	You end the magical effect outright, permanently, with no roll and no spell slot. If it was a ward, a seal, or a curse on a place, it is simply over.
19	The Real Question	Legendary	You understand not just what the magic does but why it is here. The DM gives you one genuine secret about the plot behind it.
20	The One They'll Talk About	Legendary	You solve an arcane problem that was meant to take the party a session. The obstacle is gone, and any spellcaster who learns of it treats you as a peer from now on.

Questions

Is a natural 20 a critical success on a skill check?

Not by the rules. Criticals apply to attack rolls. A 20 on a check is a 20 — which is why a spectacular roll so often produces a shrug. This table is the house rule that fixes that.

Does a natural 20 automatically succeed?

No. On an ability check there is no automatic success — if the DC is 25 and your total is 22, you failed with a 20.