Part 99: Bonus Update 53.5: Dragon TowerBonus Update 53.5: Dragon Tower
As ultrafilter mentioned in the thread, while Dragon Tower is physically located on Cloudside, the game considers it to be part of Darkside (as it does with all the other World of Xeen postgame areas). This means that Town Portal will give you a list of Darkside towns, and if your party dies then you'll see the Darkside game over screen.
The tower's monsters shouldn't give too much trouble to a party that's already fought its way through the dungeons of Castle Alamar to get the key, although the fire traps on the chests are brutal, and unavoidable regardless of Thievery skill.
The tower's design isn't too complex, but it does mean that fully exploring it requres some backtracking. Still, it's worth taking the detours up the left and right sides of the tower for extra treasure and Endurance boosts.
That really looks more like a pterodactyl than a dragon to me. Oh well. If you're just interested in getting the ID card with a minimum of combat, head directly north to the statue near the creature's "eye". If you want treasure, there are some large clusters of level-boosting crystals in the far west and east, and a few more scattered around haphazardly throughout the area.
Next time, see you in Darkstone Tower!