Keeping your hands free for Flashlights and/or Magnifying Glasses while also giving you a boost to your worst stat seems like a slam dunk to me. A nominal resource and xp cost might limit it, given how many fun toys Guardians have access to, and in a Flamethrower deck it's pretty useless, but enabling you to hold Lightning Gun, Machete and Survival Knife all at the same time is pretty appealing. Not super realistic, but I'm definitely going to try and make it happen.

This card seems worthwhile with Marie Lambeau, even without any additional support. This and Scrying are the only spells with charges that can be used any time (to take advantage of her activated power). If you would otherwise not be using the bonus actions, the maximum net effect of Alchemical Transmutation would be 1 resource and 1 card spent for 9 resources gained, which is quite good.

A fantastic card that delivers on it's promises. Persistently available boosting for a fair price.

I probably don't have to stress the importance of hitting skill "sweet spots" and "guarantees". Attempting skill tests with liberal bonuses to ensure success (the typical sweet spots are: +2 for standard, +3 for hard, the guarantee is obviously enough to beat everything the bag has to offer (barring )). Boosting has been the perennial method to generate successes and Scrapper gives permanent access to it!

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Compared to its very popular brethren (Higher Education and Streetwise) Scrapper has a bit of a disadvantage in cost efficiency, watch out for this in the early parts of a scenario, if too liberally used it will kneecap your ability to play assets and events to carry you through the mid- and lategame. This is especially true for William Yorick whose deck tends to be very expensive to deploy. Seek to obtain XP weapons that grant high hit bonuses (Timeworn Brand or .45 Automatic for example!) before you spend XP on Scrapper for that guy.

There's also the consideration of which campaign you take this card in, the boost is a big hit/miss. Agility is the least tested ability if you don't routinely evade, defensively there are nearly no treacheries in Dunwich and Carcosa, so that's a bit of a waste, its a bit more useful in Night of the Zealot and Forgotten age.

If you wish to know what characters can best put this card to use, then here's a ranking:

1: "Ashcan" Pete and Silas Marsh. Both dudes have resources to spare, tend to put both stats to full use, and both lack access to better alternatives (without using Ashcans precious slots).

2: Calvin Wright needs some way to deliver consistent success and Scrapper helps with that, it's a medium priority upgrade at best however.

3: Wendy Adams and William Yorick. Wendy Adams rarely needs help with her evasion and has higher priority upgrades, if she decides to go for combat via the Ornate Bow and/or Old Hunting Rifle then she'll need Scrapper to routinely net hits, Will to Survive should be a higher priority though. William Yorick has access to Physical Training and it combos with his ability, it's just flat-out better for him unless you're desperate for agility boosting in Forgotten age.

This card is like half a flashlight that is much less flexible ("during an investigator's turn" is the important part). The second effect may sometimes be useful but I don't think I'll ever include 2 copies of this unless I know that the scenario will be adding locations as I go (e.g. Forgotten Age).

If I’m reading this right (please feel free to tell me otherwise) ‘when you would be defeated by horror, discard St Hubert’s Key: immediately heal 2 horror’ means it has the added benefit of being a single use get out of jail free card so that even if you were on 2 sanity and about to die from taking 3 or 4 horror you could still survive with 2 sanity?

I suppose it depends on when you get those 2 horror healed but I think if a flashlight can never take a shroud value below zero it would be the same principle that your defeating horror can never take your sanity below zero. It seems to make more thematic sense this way and could make for some ‘miraculous’ play especially when fighting a boss for example, you could tank the damage for just long enough to buy your team another go round without anyone dying.