How can I make the final boss of the LMOP a memorable and exciting fight for my group?

Question

This post contains spoilers for the Lost Mines of Phandelver.

I have been DM'ing a group of six new players through the dnd 5e starter set and they have just entered the eponymous 'Lost Mine' where they will come face to face with their adversary 'The Black Spider' and a fight to the death will likely ensue.

My group consists of six players (a slightly large group), so I've already been in the habit of 'rebalancing' nearly every encounter that they come across, in order to maintain the appropriate level of challenge. I've largely used this online resource as a quick way to do so. It's normally suggested a combination of either raising HP, upgrading monsters to something thematically similar (ie - Ochre Jelly to Black Pudding), or adding additional monsters.

These three tactics are fine, for most normal encounters and I intend to employ at least two of them here, raising the BBEG's HP and adding a couple of extra minions. However, in addition to simply balancing the challenge level, because this guy is 'the final boss' of my players first ever DnD campaign, I want to ensure that this encounter is 'exciting and memorable'.

By 'exciting and memorable' I mean that I would like this encounter to feel appreciably different, perhaps surprisingly so, to all of the other, fairly vanilla, boss fights that have come before it in this campaign. So far they have all been tonally pretty similar to a normal fight, just a normal fight where the boss hits a bit harder and has more HP, meaning there might be a little more jeopardy. Note: Extra jeopardy is not bad, but that is not all, or even the main thing that I would like to achieve.

I would like this encounter to behave in ways that surprise my players 'mechanically', not just 'goodness, he hits hard'. I want this final encounter to be enjoyable, not just difficult. And, I still want to stay thematically close to the original intention of the villain (not just reskin a more powerful NPC from the MM, etc.). I'm not against player death, but I don't want a TPK at this stage in the campaign (and would fudge rolls / stats, if needed, to avoid one).

So, in summary my question is:

How can I make the final boss of the LMOP a memorable and exciting fight for my group?

General advice on boss building is not without value but has already been covered in a variety of other questions. Good answers here, would include reference to the specific parameters of this encounter, and might also include personal experience of running this module, covering things like:

1. What approaches have you used successfully in your own game to make the final encounter with The Black Spider 'memorable and exciting'?

2. What approaches have you used successfully in your own game to make the final encounter with The Black Spider feel balanced against a larger sized party?

3. Based on your own experience of this encounter, which of the following approaches, that I am already considering, would you recommend?

   1. Adding extra HP - (27 hp doesn't seem enough for a BBEG for a level 4/5 party of 6 PCs.
   2. Adding extra minions - (Accompanied by four Giant Spiders - might add two more)
   3. Adding Legendary Resistances
   4. Adding Legendary Actions
   5. Adding Lair Actions
   6. Turning The Black Spider into a "Paragon monster"
   7. Giving Giant Spider minions an 'on death' chance to use their ability Web (SRD p. 379).

Currently, I'm leaning towards a combination of approaches 1,2,6 and 7. My party = LMOP pre-gens (Fighter, Fighter, Rogue, Wizard, Cleric + an extra Vengance Paladin). We play using theatre of the mind, rather than a grid.

Answer 1

I have now DM'd the final boss fight myself. So, as no one with direct experience has thus far responded to the question (though many of their suggestions were good), I've written up my own experiences, detailing what went well and what went badly. Hopefully this will be useful to the people who have favorited this question, some of whom may be currently DM'ing LMOP themselves.

1. What approaches have you used successfully in your own game to make the final encounter with The Black Spider 'memorable and exciting'?

   • We'd played the entire campaign up to this point in the theatre of the mind. Suddenly revealing a full map and playing pieces for this fight definitely added excitement and grit, it also really helped to keep track of the AOE spells (faerie fire, web, darkness etc.) rather than me feeling like I was fudging who was hit and who wasn't.
   • I decided to add hp to the Black Spider and turn him into a 'paragon monster'. As the final boss, I didn't want him going down in just two good hits, so I decided to give him two separate hit point pools of 37 hp each - when he went down the first time he 'regenerated' into a more dangerous final form (two turns per round) which really appealed to my players, familiar with boss fights in pc games, and made the Black Spider feel appreciably different to any boss they'd faced before.

2. What approaches have you used successfully in your own game to make the final encounter with The Black Spider feel balanced against a larger sized party?

   • As mentioned above, I added extra hp to try and slightly balance out the action economy.
   • I added two extra giant spider minions (bringing the total to six). Having as many spider minions as PCs definitely added to the drama and the spectacle but if the rolls had been more on my side this could have been a bit too much.
   • We used milestone levelling, so I decided to keep the party at level 4 for this fight. Fifth level would have removed a lot of the danger, half of the party would have gained Extra Attack, not to mention the extra HP, spells and proficiency bonus increase.
   • I treated the Black Spider as a fifth level caster (as opposed to fourth level), so that he rolled a second damage die for his cantrips.

3. What would I do differently if I did it again?

   • The Black Spider is fairly toothless once all of his minions have been killed as most of his spells are crowd control, rather than damage dealing (only cantrips and magic missile, melee a last resort). If I was redoing this fight I think I'd give him the option of one scroll of fireball, to be used if the fight was going too quickly south.
   • Make better use of webbing as difficult terrain in order to crowd control the PCs.

Answer 2

I meant to come back to this months ago when I ran through it on my own campaign, but what I did is:

Create a boss mechanic

I like to find something that differentiates the boss from 'just another mage'. Something that mechanically adds to the encounter in a way that the players will not have seen before, maybe even homebrewing something - often I take inspiration from MMO Raid content etc.

I took The Black Spider's flavour and ran with it. He likes darkness; specifically magical darkness. So I decided that his room would be magically dark giving the entire fight a different tone to a standard fight.

Downsides:

1. Bugbears can't see either
2. Darkness as a spell requires concentration
3. The Black Spider can't see

Solutions:

1. Replace bugbears with more spiders (Which have blindsight)
2. Have runes of darkness on the pillars (Breakable so the party could cleanse them once they found out)
3. The Black Spider can see! (The spider staff became buffed with devil's sight)

We play on a grid, so I marked the cells (a1, b1 etc) and whenever there was a successful stealth roll I kept the marker in the place the party thought the enemy was, but made a note that they moved. This made a really memorable moment when the fighter decided against saving a webbed teammate in the middle of the room in order to run around a pillar and attack the boss. The fighter rolled a crit and celebrated like he won the lottery, only to realise that the boss wasn't actually there, queue much mirth from everyone (Even the fighter player!). I also used this moment to reveal the rune mechanic, because the sword embedded in the rune and broke the magic around that pillar.

Don't let the boss die like a chump

I gave him max HP instead of average, had Mage Armor pre-cast and with disadvantage on attacks due to darkness (When they could even attack the correct spot) it made him quite hardy.

I didn't buff his damage output because the darkness made the fight a war of attrition which gave his low damage a reasonable chance of success.

Have some tactics planned

The Black Spider and his trained spider minions have fought together before, he has prepared the room with magical darkness, and he is an intelligent wizard. He is therefore going to know how to make the most of the combined abilities of the group.

Difficult terrain from webs, ranged webbing from the spiders and damage by attrition work to his advantage. They skulked around the room until one person got away from the main group, then they webbed people up, jumped on the straggler and crucially ran back to safety when the party regrouped.

The Black Spider even had a backup plan of turning invisible properly and legging it, but a stray critical hit after a poor stealth roll prevented that.

My thinking was that although he is a bit toothless he isn't actually trying to kill the party himself. If his minions can't do the job he isn't going to stick around and risk his own health!

Judge the CR

With adding a mechanic like magical darkness (And especially some of the more complex mechanics I have added on my own campaign) the effect on CR is often not insignificant.

It is tricky to judge the CR, and to be honest I wing it (I have no idea how I have been so successful) but specifically in this case the enemies being harder to hit would increase their defensive CR (There are answers on this site reflecting how to calculate that).

Overall

I was quite happy with how it went, the players seemed to enjoy the change of pace and all my other boss fights since have incorporated some kind of mechanic which has always gone down fairly well, and crucially gets them thinking about how different tactics may work rather than a boss fight just being a more difficult version of any old fight.

Answer 3

When I ran the fight, two things made it memorable. One thing I though would be memorable turned out to be boring.

Darkness

The Black Spider cast darkness and the spiders, with their blindsense, owned the party while the party's mage alternately cast dispel magic and silence in an attempt to shut down the bad guy.

Splitting the party

One of the players decided their character didn't enter the final room (I'm not sure why). So, one of the spiders closed the door and webbed it shut. This gave the players a tactical choice - open the door or attack the bad guy. I like presenting players with meaningful choices.

I was worried that the player might feel feel lonely so I had some bugbears come along and play with him (where "play" means "try to kill"). Heh.

Spiders (the bit that didn't work)

I tried to make the scene where the spiders descend from the ceiling on webs memorable and dramatic. The player's response was pretty much just "meh".

I guess spiders have been overused?

Finally

As an aside, the Black Spider escaped. After he cast suggestion and told the fighter that there was no need to fight, the party asked for parley. While talking, he moved to where he could misty step and escape, covered by the bugbears that the character outside decided not to kill.

Answer 4

My experience with bosses tends to be:

• Have Minions arrive over time (even if it's a set amount); this helps make the boss a priority and add drama to the fight (as you can lose ground if you take too long to do things.) Give Nezz an option, for example, that every 1d4 rounds he fires a blob of eggs that hatch a round later. Players will have someone (or more) divert attention to that probably.

• Have a dramatic entrance. Usually this starts with a large empty clearing or chamber; often there is something then that changes their expectations like a gate falling behind them, a wall going up between them and their foe when they see him, or they maybe have to find the BBE in the area, walking into an ambush.

---

An example. My PCs were searching a sewer area after recovering the corpse of one of their own from a cult. They entered a long abandoned room bigger than the anything else they'd seen with tall pillars and a raised platform to the side. Flashes of light came from the platform as skeletons were slowly being summoned into the room with them. The room being big meant that the skeletons would have a couple to their number before anyone could make contact.

They fought through the few skellies and started trying to climb the platform; which coupled with the summoning, whatever skeletons were left, and an unknown BBE; that small set of climb checks was much more interesting than it could be; especially because some people in armor just couldn't do it very well.

One by one they get up there, and the first guy sees a Summoning Ooze, a weird 3.5 creature at the time; charges it down a hall way only to miss and get downed by acidic attacks. The others eventually take down the ooze, but it's a big memorable fight.

Had I placed the ooze in the middle of a room, had the room been completely level, or had I had the ooze be aggressive; the fight would've been less interesting by a long shot.

---

• So with the above, consider terrain that involves more than "I run and swing at him." These are spiders! As another poster mentioned, they climb, they have stealth, etc. Change the room! Instead it's several platforms where they climb, fight off spiders, climb some more, risk falling to a previous platform. Maybe Nezz has a way of tossing off the equivalent of a tiny splash weapon for damage; and the spiders are summoned way below to climb and harass the party during the climb. Even some pews, pillars, and pits can make a big difference to a fight.

Things that require jumping/leaping, climbing, strength checks, etc; give a consequence to the heavy armored in the group that exists in the game for a reason -> there should be a draw back sometimes just like there is a giant benefit for it.

Finally, the classic, what if what they're doing isn't just about killing the BBE? A puzzle or a series of levers, a mcguffin they need, or other goal allows you to distract them with something meaningful and be "chased" while they do stuff. They may just treat it as "kill nez, then flip levers" but that's fixable if so desired.

Answer 5

I have never played the lost mines so I don't know the particulars about the fight but the fact that there are giant spiders involved is a fact that I think you can use/abuse to make the fight memorable.

I primarily play a druid in my games and one of my goto forms is giant spider. It is not mechanically a powerful form but tactically it adds a lot of advantages that I use extensively. RAW the only things a spider can do with it's web is shoot it 60ft and entangle a creature. I have spoken with my GM and he lets me do far more with webs that is more in line with the actual capabilities of spiders. Spiders can weave elaborate webs the room should be full of them if it is their lair. This should make large portions of the room difficult to see providing large amounts of cover to hid behind. Make large parts of the ground difficult terrain and make stumbling or being pushed into sticky webs a real threat.

Use the darkness the way it is supposed to be used, dim light gives disadvantage. Spiders have a +7 to their stealth. Their attacks should be quick from the shadows then retreat possibly with a hapless victim in their grasp (just because they are beasts doesn't mean they can't grapple). This might draw more victims into the webbing and difficult terrain.

Spiders have spider climb, they should not be attacking players from the ground. Attack from the roof, the walls, the webs. Players should have to struggle just to engage.

What a lot of people don't think of, giant spiders use their webs the same as normal spiders. That means they can make webbing that supports their weight that the can climb. Have them attack from the roof descending on their web grabbing players and dragging them back up to the roof. This will put players at risk of taking significant falling damage.

While the players are being harrassed by the spiders the drow can do normal supervillian things, telling the players how futile their efforts are, being an arrogant prick who assumes his minions will overpower the adventurers or blasting them with magic, making them more vulnerable to the attacks of the spiders, putting out their lights, making it creepier.

I would say play with the theme, think like a spider, fight like a spider, use the ingrained tension that theme inspires, then actually deliver on that fear. Make it scary and menacing, not just a straight up hack and slash. The players should be struggling for their lives not forming up like British soldiers, they are being ambushed and they should not be in control. That will make it memorable, just remember to give them a way to win. Movement control is a powerful tool and can quickly end in a TPK.

I am sorry I didn't endorse one of your items on your list. But you said you play theater of the mind so I thought themes and environment would be more memorable to your players than straight mechanical changes.

Answer 6

Note: I have played LMoP, but not until the end, so I haven't got experience with this fight in particular besides reading up on it.

The important part is group size

Other people have disagreed with me on this, but in my opinion the bounded accuracy of 5e has greatly exacerbated the importance of action economy in fights. As such a group of 6 adventurers has just much more control over the flow of a fight than a group of 4 would. That's why adding more enemies is a good idea in general.

However

Adding just the giant spiders feels cheap

They're there to fight the BBE, the spiders are filling that are placed there to fix the action economy for the intended group size. Just scaling the solution up for its already intended purpose should help, but you'll end up with "just another spider/goblin encounter where the players get bombarded while taking care of the mobs first". While it might work for your group, I've had too many of those 'boss fights' to still find them original. As such I'd propose to one of the following:

• Boost Nezznar: He has a fairly nice spell pool, but most of his utility spells are concentration. I would allow him to use 2 concentration spells at the same time. While this sounds overpowered, remember that this should barely increase his damage output, which comes from his non-concentration spells.
• Divert your players resources: Nezznar has a big neon sign pointing at him in this encounter that reads "don't use your single-target resources on the mobs, here's your goal". Add a few lower level drow wizards to the encounter. Have them be indistinguishable from Nezznar in the dim light and make your players have to discern who is who.