What is the lowest level character that can unfailingly beat the Lost Mine of Phandelver adventure's starting encounter?

Question

For a lot of players, Lost Mine of Phandelver from the D&D Starter Set was their first 5e adventure. The first encounter from that adventure is rather swingy, like many level 1 combats. PCs may end up victorious without a scratch, or unconscious without getting a turn.

Terminally bad luck?

Let's assume you were really unlucky, though. Really, really unlucky. Can a single character unfailingly beat the encounter, despite all the dice being against them? What is the lowest level character that could pull this off?

Assume that whatever can go wrong for the PC, will go wrong. In general, this means that they will roll a 1 on all dice rolls (attacks, saving throws, ability checks, damage, etc.) If a low roll is beneficial to them (Divine Intervention, for example), then that roll may be a higher roll.

Assume that whatever can go right for the enemies, will go right. In general, this means that they will roll the maximum value on all dice rolls. If a high roll is harmful to them, then that roll may be a lower roll.

Encounter specifics

• The PC will face:

Four goblins. Two will use a scimitar and shield, and two will use shortbows.

• The enemies use the average value for hit points.
• Starting position of Ranged and Melee enemies, and the PC (each space is a 5-foot square):

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• Any PC-controlled creatures start as close to the PC as possible. All participants start on the ground.
• The enemies have a chance to gain surprise. There is sufficient cover to try to hide on both sides of the road.
• The two melee enemies will close in. If it becomes clear that they can't get into range, they may use an Action to doff their shields and switch to bows.
• Ranged enemies will try to stay within 80 feet (the normal range of their weapons).
• The PC has beat the encounter if they are alive when combat ends and all of the enemies are dead.

Character specifics

• May be any level (1-20), though I'm interested in the lowest level character that can pull this off.
• LMOP takes place in the Forgotten Realms, so I'm going to limit sources to FR-specific and setting-agnostic official hardcover books: Player's Handbook, Monster Manual, Dungeon Master's Guide, Sword Coast Adventurer's Guide, Volo's Guide to Monsters, Xanathar's Guide to Everything, and Mordenkainen's Tome of Foes.
• Customizing ability scores, variant human, multiclassing, feats, and playing on a grid are allowed. All other variant rules are not.
• No magic items or magic item-like things granted by the DM (boons, blessings, charms, etc.)
• Spells/abilities you use before combat may only target you or creatures you control. Only spells/abilities whose effects last 8 hours or longer will still be active when combat starts. You do not get a rest between using any spells/abilities and combat starting.

Non-optimized example

The enemies can never successfully hide from (or surprise) a character with a passive Perception of 26. As long as that character can survive four max damage crits, they can cast meteor swarm to kill all enemies (even with minimum damage and a successful saving throw).

Answer 1

Level 5 Variant Human Wizard

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The Build

• The wizard has the Elemental Adept (Fire) and Alert feats
• The wizard prepares Shield, Mage Armor, and Fireball
• The wizard has 16 CON and 16 DEX (using the point buy variant rule)
• The wizard has dedicated himself to the School of Divination

In terms of derived stats, this wizard has

• 16 base AC with Mage Armor
• +8 to Initiative with Alert
• 37 Max HP
• 2 Portent Dice

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The Strategy

Our wizard has two strategies depending on their portent dice:

One of the portent dice is at least 15

• The wizard gives himself the 15+ on the initiative roll. In this case, the wizard has at least a 23 on initiative. The goblins have a +2 to initiative, so they cannot equal or beat a 23.
• The wizard is not surprised because of the Alert feat, so he can act on his first turn. He decides to launch a Fireball at the Goblins.
• Thanks to the Elemental Adept feat, each goblin takes at least 8 damage and dies.

Both of the portent dice are at most 14

• The wizard loses initiative and must tank the damage from the 4 goblins.
• When the first two goblins attack, the wizard uses the portent feature on their attack roll. Goblins have a +4 to attack rolls, so the goblins have at most an 18 to hit. Using his reaction to cast Shield, our wizard has a 21 AC, so the first two attacks miss.
• The remaining two goblins attack. They deal a maximum of 28 damage.
• On the wizard's turn, he casts Fireball and kills the goblin

Answer 2

So there's a couple observations we can make about this scenario:

• The PC will miss with every attack or cantrip: rolling the lowest possible value on a d20 attack roll always results in a miss, even if the modifiers add up to meet the armor class of the target. Conversely, while a natural 20 on a saving throw doesn't "guarantee" a successful save, it's not possible for any character to have a Save DC higher than 19 without magic items; and the lowest any goblin can roll on a saving throw is 19 on their Strength, Wisdom, or Charisma saves. So any method that relies on attacking the enemies doesn't work, nor any method that relies on a "save for no damage" spell/effect.
• Any spell that "saves for half" deals damage equal to half the dice rolled, rounded down. Enemies will always save, and the damage rolled for the spell will always be straight 1's. So the highest damage spell is going to be one that has no saving throw associated; or where the damage is uncorrelated to the saving throw; or where the number of dice rolled is uncharacteristically high for the level of the spell.
• All goblins will deal exactly 14 damage per turn, every turn. They will always critical hit, and the damage they roll will always be maximized. So any strategy used to defeat these goblins requires the PC to be able to soak (14x4) 56 damage the first turn, and 14 damage per goblin still alive after the first turn.
• If something doesn't have to be rolled, we don't want it rolled. So the NPCs will take the average on their hit points, the PC will take the average on their hitpoints (and use stat array for their ability scores), the NPCs won't roll their own death saves, etc.
• The PC will always be surprised (nat1 on Wisdom|Perception, nat20 on Dexterity|Stealth), meaning they won't be able to do anything on their first turn... unless we can do something to prevent them from being surprised

So we'll try this with a level 7 (2 Fighter, 5 Fiend Warlock) Hill Dwarf

Our strategy is going to revolve around this basic tactic:

• Tank the first 56 damage (because the PC will always lose initiative against all the goblins)
• Cast Fireball, dealing 4 damage to all goblins (8d6→[1,1,1,1,1,1,1,1]→8→halved to 4 because all goblins make their saving throws, and cannot be reduced by cover/being unseen)
• We choose Fireball because it is the lowest level spell that can deal at least half the hitpoints of the goblins in a single action. Lightning bolt might also be a candidate, but it requires the goblins to all line up in a row, which is probably not practical. Fireball also ignores cover and doesn't care whether a target is "unseen" or not, so we don't need to worry about the goblins hiding behind cover with their Bonus Actions.
• Action Surge
• Cast Fireball again, dealing 4 damage to all goblins, killing each one (as they have 7 hit points).

So now the only requirement is to attain at least 57 hit points so that the PC survives the first wave of attacks. We start with a Hill Dwarf, which gets +1 hit points per level, and also has a +2 Constitution Ability Score Increase. We'll use the Stat Array method of getting the character's ability scores and allocate them as

• Strength: doesn't matter
• Dexterity: 13
• Constitution: 14
• Intelligence: doesn't matter
• Wisdom: doesn't matter
• Charisma: 15

Charisma, Constitution, and Dexterity can be reallocated at whim, since the only requirement is to have enough health and meet the multiclassing requirements (Charisma 13+, Dexterity 13+)

We'll take the average for their hit points increase each level (so we don't have to roll it), and this will give us final hit points of 69 (14+10+9+9+9+9+9). We will also, in liu of the Warlock's level 4 Ability Score Increase, take the feat alert, which has the feature (among other things) of making the PC immune to the surprised condition so long as they are conscious; this prevents the PC from losing their first turn.

So in one turn, the PC casts two fireballs, dealing a total of 8 damage to each goblin, killing them immediately.

Now, it is possible for the Goblins to thwart this strategy by spacing out far enough that a single fireball cannot hit all of them simultaneously, but that requires them to precognitively recognize what the PC is going to do and move out of their "all 30 feet away from the PC" starting locations strategically in order to do so, so I'm going to assert that we not treat this like a concern.

Answer 3

The lowest possible level is 4

The Problem

1. The first, and largest concern is surviving the critical hits from the goblins. This typically requires a certain amount of raw bulk or tricks such as the half-orc's Relentless Endurance. I found a different solution detailed in the next section.

2. The second concern is dealing with hidden enemies since the goblins (particularly the ranged ones) will likely use Nimble Escape to hide after firing:

The goblin can take the Disengage or Hide action as a bonus action on each of its turns.

...one solution is to use area of effect spells like fireball which don't care whether the creature is hidden, but no single fireball can affect each of the goblins by the default rules for area of effects:

^{Evaluated at https://spelltemplates.com/}

...besides, fireball would require level 5, and a specific build that I will detail can bypass this concern easier.

3. The final concern is dealing damage without being able to roll anything higher than a 1 on attack rolls. There are many solutions to this concern, but I chose magic missile.

The Character

The character, let's call her Cathy, is a level 4 human (variant) who is a level 1 sorcerer, and a level 3 bard for the following features:

• a minimum of 16 Wisdom and 13 Charisma
• The Observant feat
• Knowledge of the magic missile spell
• Knowledge of the enhance ability spell
• Expertise in Perception

...and finally Cathy has succumbed to the curse of lycanthropy (describe in the Monster Manual):

A character who becomes a lycanthrope retains his or her statistics except as specified by lycanthrope type. The character gains the lycanthrope’s speeds in nonhumanoid form, damage immunities, traits, and actions that don’t involve equipment.

This means that the goblin attacks deal no damage, even with their critical hits, since lycanthropes have damage immunity.

The Combat

• To start with, Cathy is surprised because her base Passive Perception is less than 26. This means she will be hit by four critical scimitar attacks, and four critical shortbow attacks. However, lycanthropy makes her immune to these attacks:

Damage Immunities bludgeoning, piercing, and slashing damage from nonmagical attacks that aren’t silvered

• When Cathy is finally able to act, she will cast enhance ability choosing Owl's Wisdom raising her Passive Perception to 27 (10 + 3 from Wisdom + 4 from Expertise + 5 from Observant + 5 from Advantage) allowing her to detect the goblins if/when they try to hide:

When you hide, there's a chance someone will notice you even if they aren't searching. To determine whether such a creature notices you, the DM compares your Dexterity (Stealth) check with that creature's passive Wisdom (Perception) score

(from the Basic Rules)

• Cathy casts magic missile repeatedly until all of the goblins are dead. This involves her last two level 2 spell slots to kill two of the goblins (4d4 + 4 each), and each of the remaining two goblins take one full set of missiles with a level 1 spell slot (3d4 + 3 each), and then one split set with a third level 1 spell slot (at least 1d4 + 1 each).

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Improvements

This would be possible even earlier if bards had access to magic missile since the multiclass level in sorcerer is only required to pick up that spell. The extra spell slot isn't technically needed as four level 1 slots and one level 2 slot grants a total of 16 missiles which is just enough to kill 4 goblins when divided up properly.

This improvement could come from one variant rule from the Dungeon Master's Guide (though it would require DM approval):

Changing Spell Lists

Modifying a class’s spell list usually has little effect on a character’s power but can change the flavor of a class significantly.

Answer 4

Seeing the ambush and fleeing

The idea is to have 26 passive perception so that the goblin ambush can be detected, then run away.

Getting 26 passive perception (variant human rogue 1):

• Base: 10
• Get someone to help you: +5*
• observant: +5
• wisdom: +2
• proficiency + expertise: +4

*if that's a bit of an ask, a level 3 Trickster can get familiar and have it help them.

Whether or not this constitutes winning, I'm not sure as you won't be able to hurt the goblins. An alternative is being a level 4 Trickster Akakocra and flying up in the air, but again, you can't hurt them.

Answer 5

Stealth build

Goblins have -1 wisdom, which means hiding from them is fairly simple. They have 9 passive perception, and a max search roll of 19.

A level 3 Druid can cast Pass Without Trace, giving them +10 Stealth,. Goblins will then have to spend their turns searching for the Druid while the Druid escapes.

A Druid 3 / Rogue 2 can have +9 Stealth (15 dex + 2 racial = 17 = 3 dex bonus, lvl 5 = 3 proficiency, so stealth = 3 (dex) + 3 (prof) + 3 (expertise) = 9) which means when they attempt to hide with Pass Without Trace they have 9 + 10 + 1d20 = minimum of 20 stealth. Goblins cannot detect this character even with active searches.

Level 2 rogues also have access to hide as a bonus action, so they can hide and attack every turn. Unfortunately there is no real way for the rogue to kill the goblins. Their best bet would be to try and set the goblins on fire, or just annoy them until they leave.