Should I adjust the Starting Encounter for Lost Mines of Phandelver for this party?

Question

The Lost Mine of Phandelver adventure is described on its first page as "an adventure for four to five characters of 1st level." However, I will only be running three players through the campaign (or at least for the first encounter), which makes me think that some (or all) of the encounters in the module will need to be scaled back.

I'm not too worried about most of the later encounters, since for those encounters it's quite likely the PCs will have control over when they engage in combat and how they choose to do so—also, my experience with the game has shown that encounter balance doesn't need to be as precise for characters that aren't level 1—but for the first encounter, which the PCs don't really have a way to avoid, I fear that it might be too much for the party.

The encounter as described in LMoP, and my proposed change consists of

Four Goblins, two of which fight from range, two of which fight in close quarters. Each goblin has 7HP, 15AC, and an attack, whether from close or long range, that has +4 to hit and deals 1d6+2 damage. I am proposing removing one goblin, reducing the numbers to two goblins that fight in close range and one goblin that fights from a distance.

The party, conversely, consists of the following characters:

• A Half-Elf Paladin, HP 13, AC 18, Primary Attack: Longsword, +5 to hit, 1d8+3 damage
• A Tiefling Artificer [Revisited], HP 10, AC 17, Primary Attack: Light Crossbow, +4 to hit, 1d8+2 damage; OR Fire Bolt, +5 to hit, 1d10 damage. I don't know what spells the Artificer will prepare for the day, but Cure Wounds is probable, since they've told me they plan to become an Alchemist at level 3.
• A Human Monk, HP 8, AC 16, Primary Attack: Quarterstaff using Versatile, +5 to hit, 1d8+3 damage; AND Unarmed Strike, +5 to hit, 1d4+3 damage

So given the party I've described, and the change I've proposed, does that seem like an appropriate way to tune the encounter? Have I made the encounter too weak, or should I go further?

Answer 1

It's probably okay to leave the encounter as it is

There's a couple of ways to approach this question, I'll start with a crude estimation and then dial in from there.

In terms of CR

Goblins are CR ¼ creatures, worth 25XP each. Four of them add together to 100XP total, which we then multiply using the guide in the Dungeon Master's Guide (pages 82-83) by 200%, due to the total number of creatures being 4. This means that, in terms of budgeting an encounter, they are worth 200XP total. Divided over 3 characters, that's 66.7 XP each, pretty square between a "Medium" and "Hard" encounter (again, see the DMG, pages 82-83). So at least by the standards set by the Dungeon Master's Guide, this encounter is challenging, but reasonable for a party of three level 1 characters.

Some Rough Numbers about team survivability

The process by which I arrived at these numbers involved

• Calculating the average DPR of each PC against a goblin
• Calculating the average DPR of each goblin against a PC
• Aggregating those numbers together against the total HP + AC of the opposing team
• And calculating how long it would take for each team to reduce the opposing team down to 0 hit points

This is a very crude, rough estimation that only considers the "guaranteed abilities" of each creature, i.e. their direct attacks. It does not consider expendable resources, things like Spell Slots or Lay on Hands.

The results of this estimation find that

• On average, The Goblins will defeat the PCs in 5.709 Rounds.
• On average, The PCs will defeat the Goblins in 4.778 Rounds.

This tells us something important: that in general, the PCs deal more damage, and suffer less damage, than the Goblins. This aligns with what the CR calculations told us already: that the PCs are nominally favored to win the fight.

If we then consider the additional capabilities of the party (the two spell slots of the Artificer, the Lay on Hands feature of the Paladin) we can rest relatively assured in the knowledge that, while the fight isn't a guaranteed victory, a party that doesn't self-sabotage will probably win.

_{Bother me in chat if you want me to explain my methodology. Warning: it's a lot of statistics.}

Looking at the particulars

The paladin has very good survivability for their level; arguably the best possible survivability that a paladin can have at level 1 without substantial DM fiat. Because two of the goblins are melee fighters, The paladin will probably end up taking the brunt of the early hits of the fight, regardless of whether they are spotted in stealth by the Monk's [presumed] high Wisdom score or not.

The Artificer and the Monk, conversely, are probably going to have the most substantial firepower of the group. The Monk because of their efficient use of their Bonus Action to make an extra attack, and the Artificer because of their access to Spells. If they prepare well, they'll likely have access to the Artificer-exclusive spell, Arcane Weapon:

You channel arcane energy into one simple or martial weapon you're holding, and choose one damage type: acid, cold, fire, lightning, poison, or thunder. Until the spell ends, you deal an extra 1d6 damage of the chosen type to any target you hit with the weapon. If the weapon isn't magical, it becomes a magic weapon for the spell's duration.

—Arcane Weapon, Unearthed Arcana: The Artificer Returns, 2019-05-14

Even if they don't have access to that spell, they might instead have access to spells like Faerie Fire, Cure Wounds, False Life, or other spells that could have significant impacts on the fight.

All of which tell me that this fight, while certainly not being a cakewalk, is winnable for the PCs.

On the other hand

All of these metrics do suggest that, to varying degrees, the fight could be difficult. Against seasoned, veteran players that might not be a big issue, but against newer players, that could be a problem. If the players are newer, then it's probably better to go ahead with the proposed change. If the players are more inveterate though, then it's probably safe to leave it alone.