I finished running the Dragons of Stormwreck Isle(*) campaign a few days ago and really enjoyed it. On the whole I definitely recommend it to both new and experienced DMs alike (you can check out my full review here). However, there are definitely some changes that I think you can make in order to make the adventure run more smoothly, as well as provide a more engaging experience for your players (spoilers ahead).
None of these changes are difficult to adopt or require that much prep - but I feel they are well worth making to get the most out of this adventure. Feel free to copy anything you like, or to change up anything you don't like. It's your adventure, and you know your players and what they like more than I do - so try to lean into whatever you think will be enjoyable for them. You can use my thoughts though to get you started though - here's what I did.
*N.B. The Amazon links on this page (marked with an *) are affiliate links. This doesn't cost you any extra, but I make a small commission from any sales - which helps support the site :)
Player backgrounds
So, in my opinion, the key to an awesome adventure is to be able to tie the main storyline into the individual stories of all your players - that way, they feel more invested in the story. Dragons of Stormwreck Isle is no different - and while useful, the pre-made character sheets leave a little to be desired here.
The ties in to the main story are quite generic (such as going on pilgrimage to Dragon's Rest, or seeking a life of adventure in general) and in my opinion can be massively improved upon. How easy this will be to do depends a little on your players and how experienced they are. In my experience, more experienced players are more likely to create more elaborate and interesting backgrounds, which should hopefully give you a few plot threads that you can weave into the main storyline.
If they're using the pre-made character sheets though, it will be up to you to come up with a few ideas which you can add to the backstories to tie these characters into the story. Perhaps they have been tasked with dealing with the undead on Stormwreck Isle - as it's bad for business, or against a certain god's wishes. Perhaps they have been tasked with tracking down a wyrmling called Sparkrender, who stole an important artefact from your temple. Perhaps you're an adventurer who heard tales of various Dragon Hoards on the Isle, and you're here to make your fortune. Whatever. But the more you can give your players a) a reason to be on the Isle in the first place, and b) a reason for wanting to go on the adventure and solve the problems put before your players, the more interesting and engaging the campaign will be.
Runara
The big twist in the story is that Runara, the elderly warden of Dragon's Rest, is in fact an Adult Dragon in disguise. On the one hand, this gives you a bit of a get out of jail free card - in that if there's ever a point where the whole party is killed, they can wake up back at Dragon's Rest, having been saved and nursed back to health by Runara. Ok, so I get that this is a starter set, it's designed for new players - so having these kind of back ups helps to ensure the players aren't immediately killed off and end up hating D&D. Fine. The problem though, is that having Runara as a Dragon in disguise ruins the whole story.
Think about it. If there's this super important task that needs to be done to stop immeasurable power falling into the wrong hands, and that the lives of numerous people and creatures across the Sword Coast are all at risk - then why on earth would Runara, an Adult Dragon, entrust this task to a bunch of low-level adventurers that she barely knows and who may well die in the attempt, when she herself could go and take care of it easy-peasy? It doesn't make sense. And maybe I'm being a pedant here - but that kind of enormous plot hole would really annoy me and destroy some of the enjoyment of the story.
The solution? Have Runara be just who she seems to be - a kind, wise old woman. Nothing more. If you still want the get out of jail free card to ward against Total Party Kills? Then Tarak, the herbalist from Dragon's Rest, could have been following the party and administered healing potions while they were unconscious. They wake up in a cave he dragged them to, or whatever. If you run the encounters as written, I doubt this will be necessary - but it means you have that level of insurance, without undermining the entire story.
Other NPCs
I also feel the other NPCs in this adventure could use a little tweaking, to try to encourage a little more roleplay with your players (full disclosure, heavy roleplay sessions aren't everyone's cup of tea, so don't try to force this. But being able to give your players that opportunity to express themselves is important). Firstly, I had fewer Kobolds at Dragon's Rest than the book mentions. As written, there's just too many to keep track of, and none of them are particularly interesting.
I kept Myla the tinkerer, and fleshed out a little her relationship with her brothers, who had gone to serve Sparkrender. I also created two more kobolds - Felix and Fenrinn. One of whom was a rather pompous kobold chef, who thought the adventurers were visiting Stormwreck Isle to taste his cuisine (which in reality was terrible) and the other who was a somewhat marginalised and looked down upon kitchen-boy. These two added a little comic relief to the adventure - and a chance for my players to teach these Kobolds a few recipes and the like. Obviously you can come up with different personas for any you create - but a smaller number, with more distinct personalities, worked well in my experience.
I liked the characters of Tarak and Varnoth. I spent a little time fleshing out their characters a bit more as well. What they had done in the past, why they'd come to Dragon's Rest, how they got on with each other, what they knew about Sparkrender etc. I didn't do much prep here - just a few lines of background, which made it easier to roleplay when my players started talking to them.
I also introduced a couple more NPCs - a couple of bootleggers, who were brewing potions in a cave on Stormwreck Isle (they were doing so because of the potent ambient magic surrounding the isle), and also a crew of pirates, shipwrecked on the isle, who had been turned to animals for stealing from a cursed Dragon's hoard.
I felt in general that the adventure as written didn't give enough opportunities for roleplay (which I enjoy as a DM, and could tell many of my players did as well) so I introduced these characters to right that balance a little. Whether you feel it necessary will depend on how comfortable you are roleplaying as DM, and how much your players enjoy that - but it's worth thinking about.
Improving combat
Ok, so if you're a first time DM, you have a lot on your plate just remembering the rules and trying to move the story along etc, so maybe ensuring that your combat encounters are absolutely the best they can be isn't your top priority. I can sympathise. In that case, running the encounters as they're written is absolutely fine, and your players are still gonna have a good time. That said, if you're a more experienced DM (or a beginner who just wants to push yourself) then there are absolutely a number of things you can do to make combat more fun in this adventure.
Firstly, those zombies. These are gonna be the first enemy your players encounter, and the very first experience they have of this campaign (and perhaps of D&D in general) you wanna make it good, right? So, think of a zombie from any popular culture reference in the past 40 years - how do they attack? They bite right? That's what's scary about them! The fear of being eaten alive and turned undead yourself. So, why oh why, is the zombie's only attack in 5e to slam you? What does that even mean? Are they giving you a vigorous chest bump like a couple of basketball players? Come on. Make your zombies bite. When I did it, I gave their bite a d6 of piercing damage, but then a player also had to roll a DC10 constitution save, or they would be infected with the undead illness - but they had 48 hours to drink an antidote before they would turn undead themselves.
The good news is that Tarak has one (or more. whatever.) antidote ready at Dragon's Rest, and can brew more of them if you can get the necessary ingredients from the Seagrow caves. Immediately, this gives the players a reason to really want to go to the caves, or to the Compass Rose to try and lift the curse - which all adds to the engagement in the story. It also raises the stakes of that initial battle, because nobody wants to become a zombie, right? A very quick fix, but it has a big impact on your adventure.
With the following combat encounters at the Seagrow caves and the Compass Rose, I didn't change too much - I just buffed the stats of both the Octopus and the Harpy, giving them higher HP (as otherwise the combat sessions felt like they were gonna be really brief). For the Octopus, I also gave it a legendary action to release a bunch of ink and then move away undetected, without prompting an attack of opportunity (thereby making the encounter a little more unpredictable for my players).
I also tried to might the fights more dynamic than just every player crowding round the enemy and whacking it. With the octopus I had it wrap a tentacle around a player and try to drag them out to sea, and likewise with the harpy, I had it sing a luring song to try to get players to jump off the Compass Rose and into the water, or for her to grab a player in her talons and fly off/ drop the player from a height. I also gave the players the opportunity to fix the ballista on the compass rose - because who doesn't want the chance for their character to kill a harpy by shooting it in the face with a massive ballista bolt?!
I found that these simple changes worked to heighten the tension surrounding a combat encounter - and also give players more choices to make - should they attack this creature, or try to save a party member etc? In my experience, the more dilemmas like that you can give your players, the more interesting, unpredictable (and, ultimately, enjoyable) the combat will become.
The final encounter
Ok, this takes me onto the final combat encounter, where I went a lot farther off-script than in any of the previous ones. To be clear - you definitely don't need to do this. The final encounter as written will work perfectly fine, and will be an enjoyable end to your campaign - but for me, it just wasn't epic enough. I wanted to make it harder, more unpredictable, and with a genuine chance of killing a player character or two, in order to bring the campaign to a really satisfying conclusion. If that sounds fun, then here's what I did.
Firstly, I changed the nature of the encounter. Now they weren't just gonna be fighting Sparkrender the Blue Dragon Wyrmling, but also Sharruth, the Adult Red Dragon who is mentioned in a couple of places throughout the adventure. Throughout my sessions, I'd alluded to the fact that although Sharruth had been buried out at sea hundreds of years ago, that perhaps they weren't dead - but rather imprisonned there, beneath Stormwreck Isle (and that, in fact, that it was Sharruth's presence that had caused the volcanic isle to spring forth from the sea to begin with).
Sparkrender's goal, therefore, wasn't to just bring back the spirits of ancient Dragons - but actually the physical embodiment of the biggest, meanest of all these dragons. More epic, right? More at stake, right?
And if you can allude to this throughout the adventure (rumours of Sharruth's survival, an ancient tome here and there of people trying to find Sharruth, earthquakes or eruptions alluding to stirrings underground - whatever) then the reveal at the end will be waaay more satisfying than if you just spring it on your players without any foreshadowing.
I also completely did away with Aidron, the Bronze Dragon wyrmling who had battled Sparkrender and been imprisoned beneath the observatory. I felt he didn't add much to the story, and, frankly, I wanted my party to be the ones battling for glory at the end, not an NPC that they hadn't met until just then.
Finally, I made some changes to the place where this battle took place. Basically I initially used the map of the observatory for my players to come across the stirges and a few kobolds - but then had one of the kobolds run to the higher tower before my players could reach them, in order to warn Sparkrender that people were coming to disrupt the ritual.
Once the party eventually made it to the tower and figured out how to get the concealed staircase to appear, it descended for a really long way - perhaps 150ft. On the descent my players could hear the sound of the crashing waves outside getting louder as they descended, and then disappear completely, as they realised they were descending below sea level.
As they went down, the temperature also gradually increased, until they arrived at a large underground chamber with a river of magma running through the far end of it. In the middle of the cavern was a plinth with draconic icons carved on it, and Sparkrender performing the ritual, with a few kobolds around observing him. Having the final battle in this chamber was way more interesting and gave different options to me than if I'd had the battle in the observatory itself.
During the battle, Sparkrender immediately set the Kobolds on the party while he finished the ritual - and the party dispatched them without difficulty. They then fought Sparkrender himself, but as they started to do so, he completed the ritual by placing a magical item into the plinth and the cavern floor beneath them began to shake.
Now, the whole battle map I'd divided into 20, and after this point every few goes I would get a party member to roll a d20. Whichever grid square that corresponded with would then disintegrate - revealing a boiling pool of magma 50ft below. Any characters who were on that square had to make a DC12 dex saving throw, or they would begin falling to the magma. If that happened, it would take one whole turn for them to fall to the lava - so they and the rest of the party all got a chance to save them before they did so.
(behold my terrible map-making skills! I'd painted a pool of magma on one sheet, then divided my actual map into 20 squares which I cut up and blu-tacked over the top. Whenever a certain square was rolled, it crumbled into the lava, and anyone standing there had to make dex saves or fall towards the magma. If I'd had more than about 45 mins to make this I could have done a better job - but it worked well mechanically, and you get the idea!)
The party managed to kill Sparkrender pretty easily - but meanwhile, Sharruth herself began to emerge from the magma. First just her head, then one of her wings, then the other etc. I paced it so that it would take several rounds for her to fully emerge from the lava - meaning that some of her attacks were neutralised (as she wasn't in melee range) yet her breath weapon was still a big threat. In fact, I slightly altered the saving throw DCs for Sharruth as well as marginally reduce the power of her breath weapon for fear of just one-shotting a bunch of characters (but she was still a real threat to them, and almost killed a couple).
Now obviously, trying ot fight an adult dragon as level 3 characters would be suicide - but as this was going on, as well as the floor disappearing piece by piece, the ceiling overhead also began to crack, and sea-water flooded in from overhead. Where the seawater hit the magma below, it began to solidify - with Sharruth letting out screams where the magma was turning to rock around her.
The point was for the party to realise that to defeat her, they needed to bring down the ceiling and flood the chamber - thereby imprisoning Sharruth in the magma/rock as it hardened. This led to some awesome moments, as players almost got killed by Sharruth herself, almost fell into lava on a few occasions, had to race back to the stairs they'd entered by before the whole chamber was flooded, and having the chance to sacrifice themselves by flooding the chamber while they were still inside.
It was an epic battle. 3 characters were a hair's breadth from dying, one tried to sacrifice himself by bringing down the ceiling as he was falling into lava, only for others to go back and save him. In the end, everyone got out alive, and Sharruth was imprisoned in the rock beneath the waves. I was honestly so happy with how the session went, and think it was one of the best I'd ever run. It was particularly enjoyable seeing how invested my players were, and how engaged they were in each new development of the battle - trying to keep a bunch of different plates spinning and deal with several problems simultaneously, while the whole time the tension was gradually ratchetting up.
Do you need to do all this re-writing? No. Do you need to make Sharruth the ultimate villain instead of Sparkrender? No. You can run Stormwreck Isle(*) as written and have great fun doing it. But in my opinion, a final battle against Sparkrender would have been far too easy, would have been over too quickly, and would not have really challenged my players.
By making these changes, I made the outcome far less certain, far more challenging, and (in the process) far more dramatic. You don't have to make these changes, you can do something totally different - but they really worked for me, and might be a fun starting point for you to think how to tailor this adventure to really suit yours and your players' interests.
Have fun!