... My buddy skipped 2e and never really got the hang of 3e. He got the idea that monsters have levels and it pretty much stopped there. So he tossed 20 kobolds with a kobold leader who was a 3rd level fighter at our 4th level party. After we picked our jaws up off the floor (both metaphorically in real life and literally in game) we explained to him what CRs were. But that's a 1st edition DM for you. "What's cool" is #1 and if it results in a TPK or dungeons with a magical no-teleporting field that doesn't exist anywhere else in the game world, then so be it! ....