Gloomhaven: Crimson Scales
A BBEG has summoned a bunch of imps in a swamp, and it's up to your heroes to defeat him. The Crimson Scales scenarios typically add an interesting twist to the their scenarios, and, in this one, not only are you fighting a boss monster, but you can choose one of three sets of allies to defeat him! Each attempt was tense, as the BBEG could summon another imp minion for his action, initial attacks against him were only a few hit points, he wore down the heroes to only a few hit points, and it wasn't until the last round where the heroes did significant damage. Also, the allies are good enough to kill a few minions, but were laggards and often only did damage during the last round! One of the character's Personal Quest was to kill multiple imps, and this scenario had plenty of them. So I played it a few times, trying out the different ally options.
Crimson Scales free PnP :
https://www.thecrimsonscales.com/Miniatures from the Wildspire Miniatures' Monster Set.
https://www.amazon.com/stores/WildspireMiniatures/page/B343BFEF-3714-440E-9750-50FC66D51848Tree terrain by Archon. KS coming on the 12th!