There are few things that Keep on the Shadowfell enjoys more than repeating itself. Those who remember that the first level of the dungeon started with a room full of goblinoids and a pit will be unsurprised to find that the second level, too, starts with a room full of goblinoids. And a pit.
This time around it's hobgobglins, the larger, better disciplined big cousin to our runty goblin friends. As the players come down the stairs, the hobgoblins challenge the players by asking them for a passphrase.
The players may indeed have a passphrase by now. A note found on Ninaran's dead body contained the cryptic words "From the ground, some magic was found", and seeing as Keep has never required any complicated mental arithmetics up until this point, players will be justified in thinking the connection between phrase and challenge is as obvious as it looks.
It's not; the room is a trap. Apparently Ninaran's "passphrase" was intended to warn Kalarel of her death. I mean, really, don't we all do that? Carry cryptic messages on our bodies, so that if we're murdered, and then our murderers travel half a day and fight through a bunch of goblins and undead to visit one of our friends, they might unwittingly inform our friends of their foul deeds?
Realistically, there's no way for the PCs to avoid a fight here. The hobgoblins will attack if no passphrase is given, and the hobgoblins will attack if they get the wrong passphrase. There's a right passphrase, but learning it involves catching Balgron the Fat alive, interrogating him, and knowing that you'll need a passphrase so that you can think to ask him what it is. So, really, that's not going to happen.
On the other hand, once the fight starts, it's not quite as hard as it looks. Two hobgoblins are obligingly standing directly between the players and the pit. If the players roll a high initiative, any of a number of forced-movement powers can knock the hobs over the edge and take them out of the fight. (The module reminds the reader about the bull rush rules at this point, just to make the point crystal clear.) It's a nice inversion of the Goblin Guard Room, where it was the players doing the falling.
The north end of the room has a caged Deathjump Spider, which two more hobgoblins rush to set free. This results in a kind of timed challenge; if players focus, it's a relatively simple matter to get to the hobs and kill them before they unlock the cage, but if they don't wise to the threat they'll have a nasty level 4 skirmisher joining the fray.
Unfortunately, the disparate elements don't really seem to come together. Mechanically, hobgoblins benefit from fighting shoulder-to-shoulder in tight formations. Between the odd starting locations (several hobs start in adjacent bedrooms), the spider and the well, the enemies will be all over the place, unable to really demonstrate their unique flavour. There's no leader or caster to provide a face to the battle, and both the pit-push and the caged spider are a little too binary - they either happen or they don't, and if the players win at these elements it's usually by the action of a single character before anyone else gets the chance to react.
 Add a Hobgoblin Warcaster in the western bedroom; this gives the fight a "face", and it adds some tactical support to help rally the remaining hobgoblins after a difficult first round. As a side benefit, it raises the challenge rating of the encounter to a level that will genuinely test the players. As we're about to see, this may be the player's only tangle with the Keep's hobgoblins, so it's worth making it memorable.