Paul asked a few questions in the comments of my Essentials-only Keep on the Shadowfell playthrough, which can be summed up as what did I change, and did I encourage my players to create the traits that they did.
First, character traits. Since I was running the adventure more or less on the fly, I had the players make characters and quickly come up with backgrounds that worked for them and made sense. When I make a campaign, I let players make whatever they want, but strongly encourage characters that will best fit and make sense. For example, in Tendrils of Fate I told them that since it takes place in the Shadow Marches (Eberron) that half-orcs, humans, primal classes, etc would work out best. I also don’t like having characters pivotal to the continuation of the campaign, since sometimes players die or want to change characters (which can go hand in hand), but like to tie them in as side-treks or optional quests. For example Devin’s character (Sand) is on the run from the authorities in Fallcrest. This might come up later if they go back, or a bounty hunter might seek him out.
In short, I like to encourage characters to define their characters at least loosely before we start running, but also encourage them to come up with new things on the way. This is fine because when you meet someone, you don’t see everything about them all at once: often new things come up the more you get to know them.
As for modifying the adventure, the first thing I did was change the story, such as it is. Initially Kalarel is trying to open up a portal to the Shadowfell, which is located under a keep—known as Shadowfell Keep—that he’s for some reason populated with various goblinoids and undead. To top it off, he’s also teaming up with kobolds far to the south for equally unexplained reasons. The adventure starts out with the characters heading to Winterhaven, getting ambushed by kobolds, and then getting tasked with cleaning them out. They go there, fight through a shitload of mostly-minions, beat up their goblin leader, and finding a letter handwritten by Kalarel that reveals the big plot. Aside from being something that only the most cliché of villains would do, I have no fucking clue why he’s working with goblin-lead kobolds in the first place.
Starting with the story, I’m more or less treating the kobolds and keep as two separate adventures. For the keep, the backstory that I’m going for is that it was built before or during the time of Nerath, and some paladins or knights or whatever showed up and destroyed the threat lurking within, and built the keep on top to guard the site (and did not refer to it as Shadowfell Keep). After Nerath fell Kalarel showed up with some direction from Orcus to rebuild the place. He opened up the sealed and collapsed passages, and has spent a good deal of time fixing them up so that he could try and re-open the gate. Simple, easy, somewhat logical. How do the kobolds fit in?
They don’t.
The kobolds showed up on their own and have been raiding caravans under the rule of a white dragon and his right-hand man, Irontooth (who is not a goblin, but a kobold that got badass by eating an iron dragon’s heart). There’s no letter in the lair with Kalarel blatantly explaining his villainous cliche. At best, Kalarel is aware of the kobolds, and doesnt give two shits because it provides an adequate distraction for the citizens of Winterhaven. The player’s catch wind of the larger bigger due to rumors of undead shambling throughout the woods and nearby farmland. Since the only structure north is the keep, it provides a clear heading. You could also tie it in with any player running a divine class, giving them some kind of vision, or having to head out there because a family member was torn apart by zombies and you’ve gotta foot the bill for her burial. There are ways to elegantly have the players become curious about the keep without explicitly telling them that the BBEG is lurking there with a haphazard army of goblins, hobgoblins, and some undead for good measure.
To address the numerous complaints of repetition and grindage, I compressed things. Players only need ten encounters to level up, not counting major quests and multiple minor quests. So by making the kobold lair and Shadowfell keep major quests (which they get by going to Winterhaven and talking to NPCs), I can remove at least two encounters. Also since the kobolds were raiding merchant caravans, I also made returning their goods a minor quest. Finally, if the players got to the dragon graveyard, they can find an optional item there (dragon skull) to make things easier for them later, as well as get a bit more XP under their belts. Really the only reason I’ve even going for two-levels worth is because I want to try and keep them up to snuff for subsequent adventures.
Finally it’s just a matter of fixing the encounters, requiring a combination of refurbishing the maps and repopulating the monsters (especially the kobold lair and ALL of the keep). Outside the kobold lair is mostly fine, I just added a wyrmpriest working on a magic item in the magic circle (which grants bonus cold damage), and made the river a bitch to get over without using a log bridge. Combined with rocks for cover, this let ranged characters busy themselves trying to pick off the spear-chucking, spell-slinging mobs while the melee characters close the distance to the dragonshields and skirmishers. I think it lets the roles shine a lot better this way.
I redid the entire internal part to be more consistent with a cave system, such as elevation, rock formations that can serve as difficult or even hazardous terrain, and areas where the characters had to squeeze to get into. To make things easy and neat looking, I’d pick up a pack or two of cavern Dungeon Tiles. Since kobolds are allegedly notorious for rigging traps, I’d add some of those in and/or between encounters, such as cultivated mushroom patches that explode, pits, spears, perhaps something that dumps an ooze on them. They can serve as a warning system and soften up the party. With a more expansive network of tunnels, kobolds can attack and flee from multiple directions (perhaps coaxing characters into traps). I had some thunderstones setup at the start that would not only alert the kobolds, but also drop stalactites on them (which Sand easily noticed). Finally, as I mentioned before Irontooth became a kobold that had, “consumed the heart and blood of an iron dragon,” and overall the entire clan was lead by a white dragon. A much more satisfying finale, methinks.
For the keep, the ruined foundation is going to serve as “floor one”. The crumbling foundation and buildings can work great for providing cover and difficult terrain. The underground passages are still there, they just won’t be lengthy hallways that terminate into massive chambers with randomized functions. I’m going to use pillars and crumbling walls to shake things up, as well as try to have multiple paths to each room to allow for dynamic movement. Since I only need to squeeze out about 7-8 encounters (counting traps and the like) before I can wrap things up, I think I’ll have a catacomb floor and a temple floor with about 4 encounters a pop.
As for monsters? I think I speak for a lot of people when I say no. Fucking. Goblins. None. Nadda. Kalarel is the high priest of the demon lord of the UNDEAD. There are numerous things he can use that fall within the 1-3 level range. Kalarel is a fucking necromancer. Use it. Also? What about cultists? You could cultists fill in the niche for living adversaries if you really must (I plan on allowing them to issue free commands to undead, ala the warlord class). Hell, let the party capture one alive and he can fill in some details. The idea of a cowardly farmer-turned-cultist spilling his guts (before he literally does) is much more feasible than a notarized letter in the hands of a goblin. Finally, since Kalarel is a spellcaster, feel free to mix in arcane traps. Glyphs that incite fear or weaken targets, grim totems that cause attack or defense penalties when characters are too close (perhaps they even scream, causing a push effect). The keep is ancient, so you could also use mundane traps like collapsing floors or ceilings, and if you wanna pimp the undead theme, you could have undead lying in ambush within sarcophagi.