The best that Adventurer's League Season 1 has to offer
Set almost exactly at the halfway point of Adventurer's League Season 1, "Tales Trees Tell" offers a very welcome departure from the formulaic outings up to this point. It finally breaks with the "investigate phase, dungeon phase" model to instead offer a well-executed excursion into atmospheric horror.
This adventure takes the party to the Quivering Forest, north of Phlan. The first half details a growing sense of menace in the town of Kabel's Hill, located on the edge of the forest, while the second half covers a journey into the cursed forest itself seeking out a terrifying and memorable fey...
There is simply no other adventure in Season 1 of AL that does atmospheric horror as well as this. The season's last real excursion into horror, "Shadows Over the Moonsea", really didn't work (and had more than a little accidental racism), while "Dues For The Dead" had lots of undead but little horror. "Tales Trees Tell" hits all the bases - effective flavour text, genuinely horrifying scenarios, strong pacing and escalation, and meaningful ways for the players to interact with the horror rather than merely being mute witnesses to it. In fact, it's such an escalation in horror for the adventure path that it comes with a unique warning in the introduction that less robust groups may need some aspects softened.
The adventure has a flexible approach to combat. For talkative groups, almost all combats are avoidable, but those hankering to shed some blood will be treated to some unusual and interesting monsters (including the rarely seen Scarecrow) which is great news for those tired of killing yet another kobold or yet another zombie.
The adventure uses only a few named NPCs, and the module gives you a good grasp on their concerns and motivations and how to use them interestingly. The friendly NPCs are good enough, but both the core villain and a certain fiendish wildcard are season standouts.
The module as a whole is very flexible, filled with digressions that can be easily chopped off without feeling like the players are missing much, yet adding flavour where the GM or players want to invest. That should be standard for the limited-time AL format and yet in practice it's rare enough to be refreshing here.
For all of the above reasons, this is the adventure Season 1 really needed at this point. It's a great change of pace for a group playing through the entire season, but it's self-contained enough to be run as a one-off with few changes.
The module is not without flaws. None of them greatly impact by opinion of it.
At the outset, let me say that the title is misleading. No tales are told by trees. In fact, there are no talking trees at all. Minus ten points to Gryffindor.
Moving on: it has a lot of typos. Few of them cause problems, but it's always unfortunate in a commercial product. The author has never returned to fix them despite repeated notifications of them over the years.
Secondly, it's missing cartography. This isn't a big deal, and it's par for the course for Season 1, but a handout showing the relative positions of Phlan, the Quivering Forest, Kabel's Hill, Greenhall and Jeny's clearing would go a long way. (Especially as the players find exactly that map in the possessions of multiple NPCs during the module.) Arguably the lack of geographical detail adds to the fairy-tale feel of the plot, perhaps.
Thirdly - and now we get to more serious concerns - there are some motivational issues in the module. The players know that the first person who entered the forest was making a mistake. They know that the villagers following him in was a mistake. Why would they go in themselves? NPCs such as Serelis repeatedly tell them not to enter the forest, and it's hard to argue that they're not right. DMs will need to do work to pick up the slack here.
Further, the module wants the players to visit Greenhall to learn the way to Jeny's glade, but the whole Greenhall section is problematic. The body on its borders is a fairly reasonable warning the elves don't want visitors, and they're elves - players may feel disinclined to try and "beat the information out of them". Plus the whole encounter is a bit boring, and the perfectly healthy elven village undermines the menace of the forest a little. Depending on time and pacing, DMs should either have the players' guide (or map) lead them straight to Jeny, or replace Greenhall with other Quivering Forest spookiness.
Finally, despite attempts, the adventure doesn't tie particularly well into the larger campaign. In theory, it should be a core adventure - there's a magical pact protecting Phlan's safety, it's tied in with the history of the Lord Protectors, Kabel Hill is an important trading post and warning point, the Cult are involved. Yet the events of Tyranny In Phlan (DDEX1-10) will happen whether a pact is struck or not, which rather undercuts events. There's further problems in the idea that the players might fight her for the finale. As a one-off it's not a big deal, but her stats as-written don't exactly sell her as capable of killing an entire Netherese army (as she's said to have done), or of protecting Phlan if a new pact is struck. Also, she returns in future modules, requiring some fancy footwork to cover her resurrection if players have previously murdered her.
If you're running AL Season 1, look forward to this one. It's not as epic as "Tyranny in Phlan", but it's a solid high point for module writing in this series, and should be applauded.