Dragons are Dying Constantly
Dragons are a staple of D&D, obviously. A ton of work has gone into creating an interesting variety of dragons, and providing stats for every kind at different ages. If you want to put a dragon in your game, you have everything you need to do so. That being said, dragons get killed, a lot. There is no other creature I have had my groups encounter that will consistently get murdered even when I didn’t think it could happen. The creativity of the players I’ve been around is astounding, and nothing will keep them from a massive pile of dragon loot. Here are some of the most memorable deaths.
A recurring theme I’ve seen is “kill the dragon from inside”. It’s not too difficult to get yourself swallowed by a dragon (assuming it’s big enough), and that puts the dragon at a particularly vulnerable place. Dragons are not fools, but they typically expect that taking someone out of the fight to deal with their stomach acid should be enough; no DM should think it’s impossible that a dragon would try to eat someone. Unfortunately there are a plethora of magic items that will wreak havoc on a dragon from inside. An instant fortress is my personal favourite (say the command word to cause the small metal box to become a massive adamantine tower). A folding boat will become the size of a galleon with two command words. A type 4 bag of holding filled with sand will cause the creature to suddenly find over 7000 liters of dirt in its gut. Even a bunch of immovable rods with blades attached will do the job if placed in an arrangement where the dragon can’t apply enough pressure to all at once to move them.
Smaller dragons, though still formidable, like to surround themselves with minions. This was why one party I was in decided to lure the dragon away with something in the air, and when the dragon flew by the forest we were hiding in, our barbarian managed to throw a lasso around its neck and cause it’s forward momentum to slam it into the ground (where it was summarily killed). Luring a dragon away is a great opportunity to rig the lair with traps; whether that be a few well hidden Necklace of Fireballs, or perhaps a bag of holding left open so that a portable hole can be tossed in when the dragon gets close.
One thing I’ve learned about dragons is to never expect them to survive. A DM can give them all kinds of protections and safeguards, but an experienced adventuring party, enticed by a pile of “more gold than a DM would ever want them to have”, will find a way to destroy the creature. Don’t get cocky, don’t respond with some contrived last-minute defense against their creative solution. Be fair and let them succeed if they’ve earned it. Worst case scenario, they get a million gold, and you give them an abandoned haunted castle that they can pour their money into restoring. Balance is achieved and all your dragons are dead.