This is a personal, largely spoiler free (or spoiler-vague) review of the fan-made scenario collection Mythos Deviations by The Beard for Arkham Horror the Card Game.
The Mythos Deviations are a collection of six scenarios that are meant to incorporate into the official campaigns, from The Dunwich Legacy up to The Innsmouth Conspiracy. Each use encounter cards from said campaigns (in addition to new ones), and try to take new twists on mechanics that are featured in those campaigns.
As a group, the scenarios are a mixed bag. The two strongest are History in the Making (the scenario for The Forgotten Age), which plays with exploration and the time travel theme of the campaign in a way that's very fresh, and Event Horizon (the scenario for The Circle Undone), which leans into the Azathoth theme - so it doesn't quite fit with the rest of the campaign thematically due to how that theme comes out of nowhere, but still has a fun mechanic with a lot of consideration. Both of these scenarios are strongly playable on their own, and worth playing.
Of the scenarios, the worst is Wreck of the Albatross (the scenario for The Innsmouth Conspiracy) - which has an idea to it, but fails to live up to its potential. It doesn't manage to have its new mechanic be any real threat, so the entire scenario just falls flat. The remaining three scenarios are all good - they're not quite as elaborate and fancy as you'd want for a complete standalone scenario, but will fit in the campaigns they're made for well, building on their mechanics. In terms of integrating into existing campaigns and mixing them up, they fulfill their job, especially with some of the strange rewards you can achieve for completing them. Especially as they give more XP and story assets, they might make sense into attempts on the campaign where you're playing at a harder difficult than normal, or using Return To sets you rarely do.
The Mythos Deviations set also comes with six new investigators - each one intending to be playing on the lore of one of the campaigns. These investigators have solid designs, and are worth checking out on their own even if you don't have any interest in the side scenarios.
Overall, the Mythos Deviations are mostly worth checking out, but do their best when used as their design intent - as part of an existing campaign.
More on Mythos Deviations:
Mythos Deviations: Overall
Lines of Reality: Review and Rewards
Pictures at an Exhibition: Review and Rewards
History in the Making: Review and Rewards
Event Horizon: Review and Rewards
The Labours of Hypnos: Review and Rewards
The Wreck of the Albatross: Review and Rewards
Mythos Deviations Investigators