I heard expansion Lost Valley in Solasta DnD 5 limited license game is a bit more challenging well I really hope that is true.
Lost Valley definitely has far greater encounter variety, and was definitely higher in difficulty too. For instance, you hardly ran into any casters or ranged enemies in the main campaign. Lost Valley throws a lot more of them at you, and rather early at that too. People have actually complained about being ambushed by enemies that seem to be significantly higher level than the party. During the main campaign, you would eventually out-level random encounters to the point where the game decides that the enemies would just run away before initiating combat. That doesn't happen in Lost Valley, since it takes place in a much smaller map (traveling from one end of the map to the other within Lost Valley's campaign takes about 1 in-game day, compared to about 10 days in the main campaign), the lower level encounters seemingly get replaced by higher level ones instead, though venturing out to western side of the map still seemingly results in slightly harder encounters compared to the area between the starting point and the main hub city.
For example, one of the main campaign's optional endgame boss fights pitted you against a Remorhaz at the end of a major sidequest chain, which is basically kind of like a dragon in terms of threat level. One of Lost Valley's hardest random encounters pitted you against THREE of them. In my multiplayer run of Lost Valley, we ran into said random encounter at level 9 and promptly wiped to it.
Since Lost Valley is a lot more open-ended, you can end up facing endgame encounters much earlier if you choose to pursue working for specific factions immediately, instead of exploring your options as much as possible before picking a side. But because of this (and that encounters seem to have more challenging enemies on average), you also seemingly level a lot faster in Lost Valley compared to the main campaign too.
