Help- my players stay out- I need to PC-proof this complex...

[Jeremy]

Forbiddance, Teleport Block, Dimensional Lock, rearrange the lair a little, flood the lair, pay for lead or enchanted iron insets that add % to teleport rolls or block them, have the dragon move his lair (who knows how many adventurers or bards know where it's lair is now, too much of a hassle to always have to be on guard against the next would be hero), etc.

Move the dragon to a different section of the lair several rooms or levels away, so when they teleport in it's empty and they have several hours of searching and trap springing before they find him, commission or buy a glass rose from the book of eldritch might so the dragon cannot be scried.

Rig pitfalls and illusory walls for the dragon to hide behind or in or drop foes into when he snatches them up, collapse the lair for now, dig it out later and fight the pc's on open ground where you can easily out range their spells and fly away with one PC at a time snatched in your claws....

Any other ideas?

 

[Lela]

have the dragon move his lair (who knows how many adventurers or bards know where it's lair is now, too much of a hassle to always have to be on guard against the next would be hero)

Now that's a good idea Doc. I'd go with it.

He just needs some time to retrieve what's left of his horde (likely not too much) and then he can carve out a new cave in no time.

A group of ice trolls and/or frost giants (though I don't recall you liking those guys too much) have moved in long since. After a breif dragon attack (loosing a lot from the kings treasure horde) or a visit from their god (your choice) they've resetled in.

And the dragon has moved on.