This is a personal, largely spoiler free (or spoiler-vague) review of the Consternation on the Constellation custom scenario by the Mythos Busters for Arkham Horror the Card Game.
Consternation on the Constellation is a standalone scenario where investigators have to race cultists to find an artifact aboard a cruise ship, dealing with cultists, deep ones, and the dangers of the ocean itself. It's a fun, challenging scenario that asks a lot from players, but gives interesting mechanical twists in return.
The scenario starts with the mechanical twists right from the start - asking investigators to either defeat an enemy without any items, or collect clues and then parley with intellect to outsmart a foe. Players are then given a lot to do - gathering clues from locations, doing side missions that improve the chaos bag, fighting doom-gathering cultists, or hunting for the actual artifact they need. With so much to do, there's a lot of possibilities - and a lot of distractions.
While there's a few different mechanics at play, including exhausting locations to represent the ship sinking, the most interesting one is the playing with the chaos bag. The scenario requires its own chaos bag to be used even if played in the middle of the campaign, and it starts with lots of nasty numbers, and no tokens besides skulls. As different tasks are completed on the ship, the worst of the numbers are removed and replaced with symbol tokens that are of lower penalties and come with useful effects. Symbol tokens are good here, and you want to gather as many of them as you want! However, as good as they are, they might not push your victory forward - so focusing on them instead of your real goal could be a mistake.
There's also a diverging path, depending on if the players can reach an important goal before a specific point. There's a completely different climax, with completely different requirements if they do. The sheer size of the map can make this a problem - it's easy to not have the resources to complete something on hand, and to move on from it, only to end up losing the scenario just because it takes far too long to get back to it. The scenario handles its theme well - the cruise ship feels massive, and the search feels fanatic. The slow flooding of the ship is terrifying, especially if you realize you need to accomplish something in a level that's already flooded.
With two 19 XP investigators, I found Consternation on the Constellation difficult - although I could see being in a better position with foreknowledge. Higher player counts, investigators who can pass a variety of tests, investigators who have movement tech, and investigators who can split up to handle different objectives will all make the scenario easier.
Consternation on the Constellation is a thematic, challenging scenario that's well worth your time - just don't go in expecting it to be a pleasure cruise.
Rewards
Scenario Cost: 2 XP
Potential XP Gain: 3 (locations) + 5 (library) +1 (wake titan in the deep ones encounter deck) +2 (Luther Marsh or Colossal Servant) +2 (lifeboat) = 13 XP or 11 XP after cost
So some caveats apply here. The library is extremely difficult to get the XP for - it goes back up to 1i clues at the end of the round, so you need to gather all its clues on the same turn you win the scenario. If you're taking the lifeboat path, you likely won't be able to defeat the colossal servant - and if you go the Luther Marsh path, the lifeboat won't be in play. Realistically, this puts it at a potential of 6 XP, or 4 XP after cost.
As an additional reward, as long as you successfully complete the scenario, you may add a +1 chaos token to your bag for the remainder of the campaign.
In addition, if you win the scenario by taking the Tablet of Dagon, or before all of Deck 1 and Deck 2 locations are exhausted, you can add Inspector Legrasse to your deck. He's a 3 cost ally asset that gives you an additional hand and accessory slot only for Relic assets, and can exhaust to allow you to discover a clue or gain 2 resources whenever a cultist enemy at your location is defeated.