The kobolds of the edition of D&D when The Sunless Citadel was first published in 2000 were not quite the same as the kobolds of 2017. Both are relatively weak, cowardly creatures, mainly known for their attachment to dragons and their skill at trap-building. However, the current version of the kobold is a much more dangerous proposition to face in battle due to their Pack Tactics ability. Even then, each individual kobold is very fragile, so the standard kobold tactics are to shoot at the adventurers with missile weapons (preferably while the adventurers are dealing with a trap), and to then retreat and lead adventurers into their traps. Only when cornered – or in defence of their leader, or dragon – do they attack in melee. At that point, have as many kobolds attack one character as possible, to maximise the potential of Pack Tactics.
If the adventurers are smart, they’ll be in a corridor or doorway where few kobolds can attack them. If not… well, they’ll learn the importance of defensive terrain!
Note how the central corridor in the lair loops around – this allows kobolds to attack from two directions, or to engage in harassment and fade manoeuvring: where they shoot and then retreat, leading the party around and around and around.
The kobolds of the Sunless Citadel are not initially hostile to the adventurers. Instead, they give the players an opportunity to role-play. The first room the party enters contains Meepo, the Keeper of the Dragon, who has unfortunately lost his dragon! Meepo is a gift to the DM: a character that would normally be an enemy, but sees the adventurers as the answer to his prayers. I try to play him for comedy value, but comedy with some pathos.
I find good role-playing as the DM to be hard. I try to make it memorable by using voices (then spoil it by forgetting which voice I use for each character. Make notes!) In the case of Meepo, if you can imagine a cross between Marvin the Paranoid Android and Alvin (of the Chipmunks), then you’re well on the way to creating a memorable character. “You’ll fail. There’s no hope. Except… you find dragon!”
(Basing characterisations on television or movie performances is one way I come up with and remember personalities).
Meepo can lead the adventurers to a meeting with Yusdrayl, who gives you the second big role-playing encounter of the adventure. Make sure you read the description of Yusdrayl in the appendix: she’s not hostile unless provoked. There aren’t many notes on how to role-play her, but I’d keep a high-pitched voice whilst giving it more gravitas; the intention here is to inform the players that they’re dealing with an intelligent (not foolish) creature, who can bring down the wrath of numerous kobolds upon the adventurers. If the party is wise, they’ll negotiate. And thus they became part of the goblin-kobold war…
If the characters choose not to go with Meepo, they’re almost certainly going to be attacked. They can still salvage a diplomatic solution to this, but most of the kobold guards are going to be very paranoid, with predictable results.
Meepo was a popular character, who accompanied many groups through The Sunless Citadel and beyond. He was even granted his very own D&D Miniature: Meepo, Dragonlord (an epic-level miniature!) I’ve found a store through Amazon asking $72 for a copy of the miniature… (I’ve linked the listing to the picture if you want a laugh; it’s not that hard to find cheaper copies!)
Any expedition into The Sunless Citadel is likely to take several trips, with characters returning to the surface to rest and resupply. If the characters make the kobolds their allies – and wipe out the goblins – you may wish to describe how the kobolds start moving into the goblins’ chambers, and how more kobolds can be seen on each expedition. If you’re feeling mischievous, perhaps the kobolds set up a cult to one of the characters (a lesser demi-god, serving their deity, of course!) and have kobolds bowing in that character’s presence, and wanting to touch his or her cloak…
Alternatively, if the kobolds become enemies of the characters, you should consider their tactics if the party leave and retreat. Consider adding more traps to slow down the characters, adding reinforcements (a small number), and changing where the kobolds are deployed. Once things get to a bad state (over half the kobolds killed), I’d have the entire clan get up and leave when the party are absent. Then, if the goblins are still about, they start inhabiting the kobold chambers and gathering reinforcements in the same manner as the kobolds would…