Shades are tough, as are derro. Spriggans are a hard bunch to beat, too.
(Incidentally? In Oblivion (computer game) Spriggans are sexy girl/treant things (with a hate on for you and a penchant for summoning black bears to kick your ass)).
Anything, essentially, with a layer of powers that extends beyond one or two can be a real handful to DM.
Now I've had some fun with Drow, in the past, particularly in G1 (they showed up when the party was really putting the screws to Nosnra & Co.)
Having them reanimating dead giants and tossing lightning bolts down on the party, summoning Manes and other ugly bastards in to do some fighting...that was loads of fun!


