Dragon's Lair

There is so much more to add in order to call this adventure finished, but I feel like I need to touch on all points at least, before worrying about filling in the missing details.
After escaping from the kobolds, the party make their way through a fiery subterranean world toward the dragon's lair. This is where the aspects of dragon's lair actions really manifest themselves. One was to have fire elementals appear. This will keep the party sharp on their approach. I don't think they should be overwhelmed at this point, but fighting fire-based creatures can hone their tactics before confronting the dragon itself.
There is the added benefit of draining their spells and other resources, forcing them to pause for a rest prior to approaching the dragon itself. I like this idea, it allows them to rethink spell choices and so on, as well as watch the movements of the dragon in order to better face it. Given that this quest has been a dragon quest, and the final confrontation is with the dragon itself, I feel better about having them fully prepared before engaging it. If they are at their best and strongest, they will present a better challenge to the dragon, and that is what is wanted.
When the party entered the kobold warrens, the dragon was in flight to destroy the valley around the dragon cult's base. By the time they have escaped and found the lair itself, the dragon will have returned. The route from the kobold warrens to the main lair should give a glimpse into the inner sanctum from a safe location. I don't want it to reveal the full layout of the lair, just be enough to show the presence and movement of the dragon. The dragon is still restless, and will take flight each night to scour the countryside in search of attackers.
This allows the characters an opportunity to quickly search the dragon's main chamber and plan their encounter. They may find spots they can use to trigger an ambush, and with proper spells, they could potentially set some traps and snares of their own.
Again, this all needs to be mapped and plotted, but at least this begins the process.