My Play Changes - long post, warning... it isn;t meant to be a 'this is my play session' just examples for changing stuff in the Wave Echo Cave
I did very little planning beyond having 'ideas' that I would just change things when it came to the Wave Echo Cave. I had the ghouls be more like 12 that got curious with all the noise and crept through the lightless cavern complex and jump the party... one moment (doors open on the 'safe room' where PCs can bar themselves inside against threats -- which they did not do ever for some reason) there was nothing there outside the door and the next, some 15' away a ghoul appears half lite from light from the party in the 'safe room' hissing at them... Ranger shoots it with a crossbow bolt and it hisses and disappears. Later they backtrack and find themselves in a situation where they are in a defensible position and some 12 ghouls began descending on them in waves... 'like the movie Aliens'... they got concerned and reacted with somewhat being creeped out and scarred for their characters all at once (well, 7 PCs -- a special case, extra guest players -- took out all the ghouls -- maybe because of choke points and they not being able to surround the PCs effectively) but it added a sense of 'what else is bad like that down in here'.
After that, the PCs found their way to the Wraith, Moraesk, and he was fully fledged Wraith but didn't cast spells.. which was a mistake in my setup... they got very concerned (only 5 PCs this time) and followed his tacid prompts to form a 'alliance I guess, temporary as it was', because they feared his potential for killing them, then they tricked the Spector Eye into believing that it didn't need to be there anymore to guard the mine.
The Wraith thanked them for their efforts best it could or would ever do and it 'left them alone' while it checked out all the items I placed in the Forge of Spells along with USABLE tomes and scrolls on arcane historical references, an extensive collection of formula for creating different types of magic items, lists of items created by the Spell Forge in the past and tomes related to maintenance and usage of the Forge... etc, lots and lots of lore and magic item creation guides... some maps and such.
I also included some nice magic items : commons and uncommons... with one rare 'mace of disruption' which after they looked the place and eyed wearily the wraith (so happy with itself with-what now having access to the Forge of Spells after so many hundreds of years), looking it over the tomes with it's baleful eyes of satisfaction... so,... they just jumped the Wraith... Mace of Disruption worked beautifully and after a round or two, it was 'banished to the Shadowfell' by the Mace and the Cleric... I didn't actually think they would jump him that quick, but they did... they were smart enough to do that I suppose since a more powerful beefed up wraith was going to be a problem if anyone would 'use the mine' in the future...
So, jump to the Flame Skull in the smelting and 'mundane' forge room... they killed the Flame Skull and zombies but only after taking a huge hit with a well placed Fireball... thats not something I included on my own, was provided in the adventure itself without any addition. I regret the fight didn't take longer but I did award them 2 Javalins of Lightning, which we hugely instrimental in killing it, aftrer they were bombed by a Fireball spell it casted at them. Some of the zombies were caught in the blast and went down... but they needed to lick their collective wounds after the battle.
Ok, so... the only guys left, the Drow Mage got 'more fleshed out' but I didn't do much in the way of stats increase for him, it was a few magic items, since the PCs had commons, and uncommons to use on him. They entered through the doors, after having made all kinds of racked up until this point and allowing him and his other drow conspirators to hunker down and change their battle plans... The mage had the cousin dwarf to the dwarf PC with a knife at its throat via a drow warrior... the mage just grinned at the with 10 drow warriors and a portal opening up to some vast drow city on the other side, but when 10 other drow warriors and a 'female' stepped in through the portal, the decided to bolt... they gathered up some of the tomes (lore and magic item formula lists that had been lost of hundred of years) quickly at the Forge of Spells, and booked it out of there... I didn't give them any resistance... the drow are two patient for that I reasoned, at least in this specific case.
They ran to Pandalin and warned the townspeople of what they thought would be a drow raid coming... which isn't the case. The PCs have read too many R.A. Salvatore books believing that a raid would come, but that just wasn't the case... although, because of his books some of my players reacted as if the drow warriors would be too much and they FEARED the potential abilities of the female drow. They could have taken most of them though with the commons, and uncommons I gave them... they were high enough at 4th although they were approaching 5th soon but they had a sense of doom and like in real life, if you fear something you are more apt to fall prey to FEAR, possibly without a blow being landed in some cases.
Anyways... what I learned was, try to go more on the scale towards epic? I don't think it was EPIC, but slid more along that scale towards it with the introduction of the many drow then the original adventure contains.. The female didn't need to have high level stats as in the monster manual, I think I was 'improv'ing her stats at half that or a little less'. She might have been of higher rank then Nezneer the drow 'black spider' mage BUT, you don't necessarily need to just use what is given in the monster manual for either him or the female drow, or for a 'portal' between Wave Echo Cave and a Drow city of some sort.
Now the PCs are running for Neverwinter in the dead of night to 'save' some of the lore, magic item formula tomes, et etcetera, like mad... haha, through the dead of night... I guess I scared them too much!
Booooo!