I picked up Fizban's Treasury of Dragon and have been reading it cover to cover. This is my review of the book, chapter by chapter. In this post, I discuss Chapter 4: Lairs and hoards.
Look, the fact is that in D&D, high level players run the game. After level 10 (Tier 2), the Dungeon Master is no longer in control of the surroundings or combat. By Tier 4, the Dungeon Master is on the run. High level players are forces to be reckoned with, but it's a real trick to find the balance between presenting players with a challenging combat and just declaring that a sinkhole swallows them whole and abruptly ending the game. My point is that the lair action mechanic is a great way to add challenge to a challenge, and this chapter has a bunch of ideas.
Lair actions make the home turf of a monster an additional threat during combat. I don't think anybody needed lair actions to be codified or even called "lair actions," and I have the idea that many, if not most, Dungeon Masters, have utilized environmental threats for decades. But lair actions does codify the idea that when you're in the lair of a powerful and magical beast, there could be other hazards aside from just that monster. Rocks could periodically rain down upon you when your foe strikes out at you. Magical forces that have been collecting in a corner might lash out at you between rounds, or you might step into a puddle of acid when charging at your enemy.
This chapter adds ideas for combative hazards within the lair of a Dragon.
It doesn't just add to combat, though, it also describes how magic affects that region around a lair. Many of those effects have an influence on nearby populations. For instance, draconic traits may be more common among children born in the region around a Dragon's lair, ostensibly because of the magical influence.
The second half of this chapter is about the Dragon's hoard. It discusses why Dragons want and need a hoard, the logistics of keeping a hoard, the magic that becomes suffused on the hoard, what kind of treasures a hoard contains, and so on. There are several tables to calculate the contents and value of a hoard. There are story ideas for how players might interact with a hoard, quests that could involve items from a hoard, and even hints of puzzles (in the sense that players must puzzle over something) around how players intend to deal with a hoard once they've defeated its Draconic owner.
This is the kind of story that just makes me want to run a high fantasy story. Something set in Cormyr, maybe, or Dominaria, or some iteration of Camelot, with King's courts and Dragons and Halfling burglars. The section on the hoard is fun and inspiring, and I can almost hear the ticker tape rolling by as players try to calculate the weight of gold against the capacity of their single Bag of Holding.
This chapter perfectly rounds out the first half of the book. The world of Dragons has been described in just enough detail, the multiverse has been unified, and both player characters and Dungeon Masters have gotten new options with Draconic overtones. It's not the old encyclopedic Draconomicon of 3rd edition, but it's exactly what I'd hoped for from a 5e book about Dragons.
The first 4 chapters took up 75 pages combined. The next chapter alone is 82 pages, and it's titled Draconomicon.