Now unfortunately, as per the rules on Removed from Game, when Hallowed Mirror leaves play, the 3 copies of Soothing Melody are rendered totally inaccessible, since a card removed from game "has no further interaction with the game in any manner for the duration of its removal." However, there's an easy workaround for this.

Just buy 5 extra copies of Before the Black Throne. Each mythos pack comes with 3 extra copies of Soothing Melody, which would give us a total of 15 backup bonded cards. Remember, we don't have to find the 3 specific copies that came with this one specific card, just 3 bonded cards total. This should be more than enough to fuel whatever recursion games we feel like playing with Hallowed Mirror for an entire scenario.

Of course, if any 3 copies of Soothing Melody will do, why not just proxy them? It's definitely cheaper than buying whole mythos packs, and works just as well for filling out our collection with all the copies of Soothing Melody that we could possibly need.

But then, if we're not bothering to get extra copies of Hallowed Mirror, why even bother proxying? We only have 1 copy of Hallowed Mirror, so only 3 copies of Soothing Melody will ever be in use at a time. There's nothing stopping us from just pretending that, once they leave play those 3 copies of Soothing Melody have been replaced by 3 new proxies that happen to have been made with the exact same cards.

Of course, skipping all this, we can always just realize that if a rules discussion can be rendered moot by just buying 5 extra copies of a mythos pack that you then don't even have to bother opening, that maybe "Hallowed Mirror leaving play means you can't get back the 3 copies of Soothing Melody if you play it again" was never how that was intended to work in the first place.

Incredibly cruddy card.

Banish is an alternative Blinding Light, one of the top -worst- cards in the game. Banish is very fair compared to it's nephews at 0 and 2 XP.

• Damage is sacrificed to trade the negative token effect for a positive one.
• The cost is equal to or higher than the nephew cards.

If you haven't tried them yet, Blinding Light is a real chore, they are expensive, have a game-loosing token effect and a maddeningly high chance to just whiff without any in-built +. There's also the conditional element that even if you succeed, this limited and temporary a solution to an engaged enemy might just not yield the result you want, and they're right back in the next round (Rita Young very literally gets a free copy of Blinding Light every turn, except without the action losses, free of charge and some extra mechanics too).

Banish is almost as bad as Blinding Light, it's expensive and the lack of + is crippling for a one-off effect, no chance of lost actions however is a big deal and unlike Blinding Light the moved enemy will probably not be coming right back next turn, in some cases it might even be considered to be "defeated" because it lacks a hunter keyword or isn't a threat, for example if you send the humanoid enemies in Dunwich to finished locations. The nonelite mechanic is a big bug though, preferrably I'dd have liked to see the effect be able to target Elites, for that pinch-evade, just not move or extend-exhaust them.

Banish is, in the end, better than the Blinding Light duo, but that is by no means saying much. Grab it if you like the idea of getting enemies out of the way.

TL:DR, avoid like the plague unless your options are limited or your name is Agnes Baker.

The faction is one of the two most resource starved groups in the game (the other being ), powerful economy cards are great but their cost may just be too great for you to pay for. Forbidden Knowledge is one such card, for the vast number of characters the horror is just too great and they perish quickly, Agnes Baker however LOVES this card.

• 4 Resources is good, 4 horror is BAD, from what we can surmise at the moment two points of horror heal is worth a card and two resources, I.E the trade here is very inefficient, not to mention the greatly increased risks in the scenario. Almost no characters have the horror tank to endure this and those who do might want to look at other options, like Uncage the Soul and Emergency Cache, both of those grant similar resource benefits and at no horror cost.

• Secrets rarely combo, there are just 2 cards in the game that interact with this resource type and those cards are bad on their own.

So, it kills you and compares terribly to other cards, so why does Agnes like it? Heck, this card might as well be her strength card, and a 2-off at that! The main reason Agnes loves it is the fact that she can trigger the trigger outside her normal turn. With generous application of spells and being buried in enemies something like this might happen:

Trigger Forbidden Knowledge in the Mythos phase, shoot something with Shrivelling and pull a , get punched in the enemy phase taking another horror. That's 3 triggers on her ability in one turn which is another 3 points of damage on top of her Shrivelling, enough to kill bosses in solo in one round! Of course, typically, you'll perhaps not draw a special token with the Shrivelling or draw horror inflicting effects in the mythos phase, Forbidden Knowledge is very flexible so you can usually adjust accordingly. To be able to pull off combos like these you absolutely need Fearless and might need to forego a copy, or even both copies, of Arcane Research.

Pros:

Amazingly versatile: if all copies of Soothing Melody are drawn, you can heal up to 3 damage and 3 horror or 6 damage/horror from any investigator and/or ally at your location in any combination. This makes Soothing Melody the equivalent of 3 copies of Emergency Aid, or 3 uses of First Aid(3) with added card draw.

Amazingly versatile part 2: with cards such as Moment of Respite and First Aid(3) you can “waste” them by not being able to use the effects fully, for example: only healing 2 horror for Moment of Respite, or only healing 1 horror from your ally and not needing the health heal from First Aid(3). By contrast, Soothing Melody has such a variety of potential targets that it’s effect will never be wasted.

Cons:

Has the common healing card disadvantage of requiring 2 actions to play and then use, although this is mitigated by the added card draw.

Both Hallowed Mirror and Soothing Melody take an action to play, meaning you need to be disengaged from enemies if you don’t want to eat an attack of opportunity to the face.

Hallowed Mirror is extremely weak to “asset hate” cards, such as Corrosion in Path to Carcosa, requiring secondary asset protection (and backup horror mitigation if removed before asset protection in place) to ensure all Soothing Melody cards in the deck can be drawn.

Guardians usually use the accessory slot for sanity protection, Hallowed Mirror denies the slot until removed from play, requiring Relic Hunter (3xp) to gain a second accessory slot.

Hallowed Mirror is only a singleton card: sources of card draw or deck searching are needed to play it reliably, as well as the resulting Soothing Melody cards.

Similar to Emergency Aid, Soothing Melody is drip-feed healing compared to First Aid’s consistency of being able to tap when required once played.

Soothing Melody is outclassed by Moment of Respite(3) on a 1:1 comparison, as well as the combo of First Aid(3) and Emergency Cache(3), although by this point you’ve spent 6xp on two cards to outclass a single level 0 card.

Pretty sure you can stick this in a Backpack & forget about it!

Sadly, Backpack specifies non-weakness items.

But conveniently, there's still Ever Vigilant and Dr. Elli Horowitz!

Haven't gotten far in Carcosa yet, but seems pretty mild overall. Basically just -1 action if you have nothing else to help.

(Thank you @Zinjanthropus and @Death by Chocolate for comments)