I want to share my party experience of their yesterday trip to the grimlock caves as it shows how terrain advantage could outclass even a highpowered PC party ;-)
It was really a classic beat-up-the-party match where they maneauvered themsleves into a situation that was much more dangerous than designed.
The party features 6 4th level PCs (samurai, druid, wizard, psion, cleric and rogue/bard) and I did not change any of the stats given in the adventure (which - you remember - is made for 4 3rd level PCs).
Lets start after defeating the kennel master and his krenshas. The party investigates the drop-off and realized that there is a ledge on the far side of the cavern with two archers scouting. However, they could not find a way to cross the gap so they decide to go down to the cavern floor and use the tunnel there after they scare off the two grimlocks with a well placed flaming sphere.
Down they noticed the choker (good listen check) but are unable to get hold of him so they decide to ignore him for know. Both chokers decide not to headlessly attack a 6-people group.
The group then scouts the second cavern and noticed the rope-bridge. Because of their light disadvantage they are unable to figure out what is on both sides of the bridge. They managed to shoot a rope over the bridge, fastened it somehow to have something to climb up. It proves very difficult to climb up, manage to move from rope to rope-bridge and to traverse the bridge to the ledge (Balance) - exspecially for heavy armored PCs.
The first to take that route was the druid (a goreburute shifter who is not helpless in close combat). He spots two grimlocks on the ledge but not the barbarian and decided to attack. Unfortunatly he does not stand a round against 3 of them and went to -2 hitpoints.
The samurai was next but was unable to get foot on the bridge failing climb and blanace checks miserably as he got under fire from the two grimlock archers who positioned themselves on the other side of the bridge. This sends him down for some falling damage. Nobody else was able to help as they could not see to the bridge and could not see the grimlocks either. Meanwhile the grimlock pushes the unconcious druid over the ledge (I am a very nasty DM sometimes but like to make the PCs really hate me or my mosnters :-)) which brought him to minus 9 through falling damage.
The next who tries was the rogue/bard plus the restored druid. The restored samurai following close. The rogue manages to get past the barbarian to flank him together with the druid. Druid plus samurai were struggeling with one remaining grimlock plus the barbarian to get off the bridge and onto the ledge. The rogues falls prone after an attack from the barabarian. The archers were peppering the group with arrows for another round until they got distracted through a summon swarm from the druid.
Nobody down at the cavern floor remembers the chokers... The first choker gets very close to the cleric. The cleric, heavy crossbow at hand, readies his action to find something to shoot at. She does a great listen check and realised the choker just 3 ft behind her. Her crossbow nails the choker to the cavern wall. After defeating the choker noboday gave a thought on that there maybe another one...
Meanwhile the samurai kills the barbarian with his double-bladed scimitar with two very lucky strikes - both critical.
The wizard was grappled by the second choker but the aberration gots killed by a heavy augmented mind thrust from the psion.
When the rest of the party manages to get onto the ledge, the two archers are still alive and so the group now is trapped between the archers and the rest of the grimlock staff in the deeper caverns, most of them barely wounded, most spells wasted, with no chance to recover. Lets see how they will manage that next week...
Actually after the show we discussed what the best way to avoid being trapped by terrain disadvantage would be as it seems to be impossible to deal with the archers from the kennel-master hideout.