One of my favorite adventures would have to be going against "The Mountain" (well, in search of The Mountain, but the uber-mage doesn't like visitors). One of the first lines of defense of his keep is a necromatic woods - granted, this is in DnD - we were all 10 - 14 level and barely survived: Ranger, 1/2 Orc Barb, Cleric - twuz a most fun campaign, especially when the mage sent one of his underlings (still uber-powerful in our comparison) to investigate, our combined brain power was just enough to realize that we should ask first, then wait to see if she obliterated us.
I've not used the necromatic woods in any of my campaigns as a DM, but as a player, it is a lot of fun to go in search of The Mountain. Each side presents a different possibility for pain. It gives the DM a lot of flexibility too - the uber-mage is on very friendly terms with drakes, wyrms, wyverns, sylvans, grey elves, drow, etc. - so any one of them could be called upon to defend his keep and grounds.
If you're looking for a good parallel into this, I would pit the players against a forest of Hurons. I like the disenfranchised and disenchanted Ent aspect - be one hell of a tangle - both physically & mentally (do I fight this creature of yore?! Ouch!! Well, if I cut him while blocking and parrying, it's his fault - spell flicker & story teller - you two better think of something quick or else I'm going to be a pile of goo stuck on his root).
--------------------
<ul>
<li><a href="http://ghlbeyerlein.tripod.com"> My web site</a>
<li> <a href="http://stations.mp3s.com/stations/358/grutos_metallipage.html">My MetalliStation</a>
<li><a href="http://www.grid.org/projects/cancer/"> United Device's distributive computing Cancer Research Project</a>
<li><a href="http://www.firstgov.gov">FirstGov.gov</a>
<li><a href="http://www.tsa.gov/public/index.jsp">TSA.gov</a>
<li><a href="http://www.whitehouse.gov/homeland/">Homeland Security</a>