I think there's a qualitative difference between the Chamber in Eberron and draconic villains who conceal themselves and/or their true identity in order to weaken the PCs.I always felt dragons were portrayed that way. Dragon Mountain (2e adventure, dragon had many minions and used polymorph to spy on the PCs), many 3.x adventures and the 4e "mini-adventure" gave me that impression. (The latter probably to get the PCs low on healing surges before facing the big monster.)

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.