Tonguez
A suffusion of yellow
I came across Dungeon Worlds concept of Fronts - the cluster of Dangers, GM Moves and Impending Doom - that the PCs are facing in an adventure and thought they were brilliant, I now use them in all my adventure design.Not nearly enough Owlbears
But more seriously: I also feel that the Dungeon as a habitat of many groups and powerful entities, with potentially opposing interests that can be leveraged by players, could see more use.
By layering 3 or so different Fronts a GM can organise the various factions, wandering encounters and themes they want to use to tell the story. The PCs can just face each encounter or if they figure out the themes can start to be more tactical and leverage the different moving parts to counter the impending doom.
and Owlbears are awesome (iimc Owlbear, Gryphon and Aarakocra are related species)