I like very much this scenario, but ERRATA needed for true-solo mode.

ERRATA must adding "reveal Chamber of Sorrow".

Otherwise the scenario it's blocked and there's no way for a single true-solo player...

The Black Cat can negate 2 of the 3 symbols 3 times, for when you really don't want to pull tablets and elder things and catastrophically fail - you'll even have a decent chance of passing the test.

As far as weakness mitigation goes, this is rather XP expensive as Daisy's elder sign effects are quite good and don't need replacement; though the cat's soak is better than anything else she can get in faction.

Tristan is expensive, but Preston doesn’t mind expensive. For some, he can function simply as a Darkhorse that provides soak. (And they stack.) But the rogue card people associate most with two stats is lockpicks, which Finn and Trish would appreciate a perma +2 with. Playing him for free will require a table wide commitment to fill in the bag, or not trap all the tokens for other uses. At worst, it’s a little upside when someone pulls three blessed tokens in a row. If someone has two Favors in play, the trigger becomes “when a test involves a blessed or cursed symbol“ which is inevitable.

This card is excellent in a Preston Fairmont deck, taking advantage of his base value of 1 in each skill. Since he's likely to be mitigating those with cards like Dark Horse and Lola Santiago, Preston can use this on a skill test that he's likely to pass and still put several tokens in the bag.

Another signature Weakness that involves making choices. Looking at the two elements, the effect and the discard condition, we get:

The effect: This is, more or less, an Ancient Evils that costs Agnes an action and 2 resources for the dubious privilege of losing a turn and maybe advancing the Agenda. The second effect, where, if you don't play it, Agnes takes 2 Horror each turn, might seem like a way to get some damage in, but the 2:1 Horror to Damage ratio isn't in Agnes's favor, even with Horror soaks like Peter Sylvestre in her card pool. You can probably take it on the chin for a round or two, waiting for (or avoiding) the Witching Hour, but it's definitely troublesome, and, in rare cases, can cost you the game. The impact is a little dependent on whether you are in a scenario with a couple of long Agendas or a number of shorter ones, but it's never good.

The discard condition: Covered above, you take an action and spend 2 resources. Being a Spell, costs can be eased by Uncage the Soul, Shining Trapezohedron, and/or Robes of Endless Night (with the level 2 version saving you the possibility of taking an Attack of Opportunity for your pains), but that is almost always scant comfort.

All in all, this is average signature weakness, perhaps above average if you really hate Ancient Evils.