This is a pretty incredible card. Over 9 campaigns, you start to notice that the game often presents specific configurations of scenario mechanics that can all get bodied by a boot in the door:

• A scenario climax with one or two key locations, guarded by scary enemies or effects, that can be cleared by emptying out a high-shroud room (sometimes with a narrative shift or bonus for doing so instead of killing the enemies).
• Optional high-shroud challenge rooms with Victory 1 or Victory 2 attached.
• Rooms with incredibly high shroud values you can only hope to investigate by either following specific mechanics or making specific sacrifices (horror, card discards, clue expenditures).
• Needing to spend many clues for a certain effect, with a room that infinitely replenishes clues.
• Enemies or card effects tied to the shroud value of a room.
• New, in The Scarlet Keys: performing non- tests against a room's shroud value.

This is up there with First Watch in the vein of 'great Guardian utility cards your Fighter will struggle to squeeze 2-4 of into their deck'. And it's a level 0 event, so even the Tony brand of deck building can run it. You might think you specifically need high base to make it work, but almost any teammate wouldn't mind throwing one of their UCs in to the test. A good Mystic will reserve a Promise just for this; a good Rogue will wonder why Skeleton Key even exists.

By itself it's not a particularly great or flexible card, an action to play, a test to succeed, resources to pay, for the solo it can be a silver bullet for objective or victory locations, but usually it's more like skill-icon fodder and an early cut for upgrades. it's the deckspace issue that REALLY treats this card harsly.

BUT.

in multiplayer it's a whole other ballgame, the bigger the team the better. Usually in small teams you´ll cheese up the clues on hard locations with clue teck, so Breach the Door is wasted money and card-draw, but when you run into that 4 or 5 shroud location with 3 clues / investigator, even the cluevers are gonna go "uh, I need a minute". Enter: Breach the Door!

As a main fighter in a team, you might often get saddled with a dud turn, best spent regrouping, setting up, taking resources. Breach the Door gives you a neat trick to do to help the team burn down tough spots. A location with 2 clues / investigator and shroud 2 or 3? Turn it into a 0-shroud and watch as all the "flex" character and yourself suddently contribute an easy 8 clues in 9 actions, not bad i'dd say. Otherwise you might take a 4 or 5 shroud and turn it into a 1 or 2 shroud, all of a suddent the cluever does'nt need any setup at all to take care of the whole thing by themselves.

I really hope to see more stuff like this.

This is a niche card that excels in or even trivializes some scenarios but most of the time isn't very useful. Do you need to clear a ridiculous amount of clues from one location? Is the enemy's strength tied to the location's shroud? Congratulations, you've just won the scenario.

The rest of the time, it let's a Guardian help a little with clues.

The obvious benefits of Breach the Door, already stated:

• Makes it possible for even the lowest intellect punching investigators to pick up clues

• Enables the clue getters to suck up clues even faster

Not mentioned yet:

Breach the Door combines very well with cards that provide benefits for 0 shroud locations. Some examples:

• Fast action exhaust Lola Santiago and discover a clue for free!

• Apply the shroud 0 to your Sixth Sense and Sixth Sense (4) when you pull a special symbol

• No curse token cost to play Stirring Up Trouble

• Automatic activation of Shed a Light to pick up 3 clues in 1 action

Special case:

• Guardians have access to a bunch of cards that trigger the discovery of clues, but they don't have access to many investigation boosters. Breach the Door definitely comes in handy when your low intellect Guardian draws the Unspeakable Oath (Curiosity) weakness.

This card can reduce a shroud to zero. This means it can be used by a guardian with no enemies to make it to where even ones like Daniela can safely investigate even high shroud locations. It's also thematic. Frustrated you're dumb with an INT of 1? Just break everything.

It does get outplayed by other guardian abilities (lessons learned, evidence) once upgrades are available, but its a decent level 0 mid-tier card.