There are a couple issues that I see with 4e and sandbox though. It has a MUCH narrower tolerance for off-level encounters. I recall in a 2e game a few years back throwing a Hill Giant at a level 3 party. It was fun and challenging for them. One character IIRC ended up squished flat, but the players loved it. I don't think you could run that encounter in 4e out-of-the-box. I'm sure you COULD do it, but you'd have to specifically design the whole encounter to work with low level PCs. In 2e it was just a regular encounter in my sandbox that the party happened to blunder into even after they saw the warnings about not going there.
The secret passa ge was there already.
Good call in putting in a beholder. With MM3, you could even put in multiple beholderkin.
Another part of H2 I liked was thr Horned Hold. Not the encounters themselves, but the map for the Hold was very good, and a good example of an underground dwarven fortress.
Me, I wish WotC would do a conversion of the Forge of Fury.
I actually think 4e is much better for off-level encounters than was 3e. In 4e you can set 3rd level PCs vs an 11th level hill giant brute and they'll probably survive. In 3e if you set 3rd level PCs vs a CR 7 hill giant, or even a CR 5 troll, the monster will be killing at least one PC per round and will probably TPK them. Until you get 10+ levels above the (low level) PCs the usual problem in 4e is monsters that can't be hurt, not monsters guaranteed to kill the party. So, use plenty of high level brutes in your random encounter table & you should be fine.![]()
I actually think 4e is much better for off-level encounters than was 3e. In 4e you can set 3rd level PCs vs an 11th level hill giant brute and they'll probably survive. In 3e if you set 3rd level PCs vs a CR 7 hill giant, or even a CR 5 troll, the monster will be killing at least one PC per round and will probably TPK them. Until you get 10+ levels above the (low level) PCs the usual problem in 4e is monsters that can't be hurt, not monsters guaranteed to kill the party. So, use plenty of high level brutes in your random encounter table & you should be fine.![]()
)What elements would make an adventure more exciting than another? What is missing or wrong in those adventures that fall flat? The primary common element I see is linearity and "obligatory" content. Is there anything else?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.