It seems like our adventurers have been in this Iron Tower forever. All of that is about to end, especially as the three have awoken the dragon, the mutated, angry, charging Iron Dragon.
The party works for a museum that wants to recover a long-lost solid gold holy symbol of the sun god from a long-deceased dragon's hoard. Recently discovered maps place the dragon's lair on an island off the coast. They'll have to move quickly, because their rivals - a dwarf/gnome duo of mercenaries - got to the information first and plans to sell the holy symbol to the highest bidder.
But that's not all. The island has recently been bought and reworked by an eccentric wizard as an arcane zoo, featuring dangerous monsters from across the realm. It's not open to the public yet and security is very high - but there's a private tour for wizards only, and that's an opportunity to sneak in. The name tags for the tour group allow access to the park's teleportation circle network. Turns out that the mercenary duo had the same idea, and are also using the tour group as cover.
The park's security centre should hold all the information the party needs to bypass the wards and find the dragon's lair, but the building is heavily guarded and protected. The PCs will need to slip away from the tour group and find the park's plans in the security centre without being spotted, then decode the arcane script piece by piece as they make their way through the defenses. Once the players access the dragon's lair, they'll have to carefully pick their way through the ancient traps to find the hoard. The dragon was so greedy that the final trap animates its skeleton to protect is loot even after death. This is probably a good area for a confrontation with the mercenary archaeologists - they can either steal the holy symbol and force the party to chase them down, or the party gets the artifact and the mercenaries will hound them the rest of the adventure.
Upon exiting the tomb, all hell has broken loose. The zoo has been sabotaged and the monsters are roaming free; the network of teleportation circles is shut down. A few of the park employees have defected and are in the process of stealing the unique ward spells the wizard wrote to build the park. A group of thieves has taken the tour group and the wizard hostage and is sending out men to try to find a treasure hidden somewhere in the zoo - the artifact of the sun god. And to make things worse, a major storm is brewing.
The party's objective is simple - escape the island with the artifact. But now they have a whole slew of complications in their way: hungry roaming monsters, rogue employees, a coordinated thieves' guild, a rival archaeologist team, and a big storm. They also have two additional opportunities for heroism or loot in the wizard's spellbook and the hostage scenario.