There are already reviews written like you have purchased all cards in the game to pick from, so this one is in perspective of newer players arbitrarily buying Investigator Expansion as they like.

Mandy has similar vibe to Vincent Lee and Carolyn Fern that the ability can't work on its own, and the Investigator Expansion box that give you the investigator doesn't give you many Lv. 0 card that trigger the ability to get start with. No choice of subclass (, , ) adds any more search card for her either. (But to be fair this TDE box adds a ton to Daisy Walker...)

For Mandy, you get just Practice Makes Perfect (while Otherworld Codex is Lv. 2), and a new Practiced card is just The Eye of Truth Lv. 5. You have Deduction, Perception, and Overpower (that you might try committing for friends) to work with Practice Makes Perfect. You can get Versatile to add one Vicious Blow but that's a big stretch.

The designer seemed to think that since there is Old Book of Lore in the core set (and Lv. 3 in Revised Core Set) Mandy is minimally playable, but this is further gimped by how Research Librarian's full deck search will immediately get canceled by Shocking Discovery. Trying to draw into the book could just run into Research card like Astounding Revelation (which you are aiming to add secrets to Old Book of Lore (3)) too, making you sad.

Even if you want to work with other player's search card, there are only Tetsuo Mori (might be your savior to find Old Book of Lore without Research Librarian), Lucid Dreaming, and Arcane Initiate (which is quite potent to use her ability on). So if you have small collection, I recommend teaming up with using Tetsuo Mori or using Arcane Initiate so there is less downtime of her ability.

Now if we look at what Investigator Expansion you could own prior to The Dream-Eaters that would greatly expand Mandy, I think it's The Path to Carcosa Investigator Expansion. This box gives Eureka!, Calling in Favors (which Tommy Muldoon can also make use of), On the Hunt (for other deck), and No Stone Unturned / No Stone Unturned (5) that could search. Carcosa also let Practice Makes Perfect + Mark Harrigan popular combo happen, to play with his Vicious Blow and The Home Front. I guess Quantum Flux could be handy for subclass choice to bring back Research cards back to deck all at once for more searches. subclass also gets Resourceful for use while investigating. Lastly, Minh Thi Phan in the box can add a commit icon to Brute Force, Sharp Vision, Expeditious Retreat, and A Glimmer of Hope. Plus she is on Extensive Research art so I guess they are good friends.

It’s kind of like Runic Axe, except you can’t regenerate 1 ammo per turn, you can’t spend a 2nd ammo to get +2 Combat, you can’t choose to deal 1 less damage in exchange for +2 Combat, and once it’s out of ammo, you can’t fight with it at all.

But you DO only take up one hand slot, so there’s that.

Honestly I think this is undercover one of the best cards in the box. It seems okay, but in all of my play experience with it so far it’s almost guaranteed to heal horror every single turn, it just works out. Just horror soak alone might not be totally enough to justify spending 2 and an XP (it’s pretty good though), but it just has more practical purposes. Obviously it came out with Chemistry Set, and it’s very useful there if you’re going the full asset route. But there is just so many other benefits. I would say first and foremost this is an auto include for Rex. Turning Rex’s ability into succeeding by 1 instead of 2 because you have Steady-Handed makes life easier, plus the horror soak. Deduction 2 is also safer. Grim Memoir is even more likely to draw a card. If you don’t need the healing you can just bump up your success to get more growth on your Ravenous Myconid.

There are certainly extra benefits if you can play rogue cards as well, because of their succeed by 2 archetype. All of the sudden you have safer lockpicks, your weapons are more consistent. Your Quick Thinking is more likely to give you an action. Consistent horror healing for no action cost helps cover for damage taken through your low willpower. I think Trish loves this card. I think Roland could also love this to help cover for his sanity struggles.

If you haven’t really tried Steady-Handed, I suggest giving it a shot, especially if your deck has proactive synergies and don’t have it exclusively for horror soak.

Two draws are significant because not only you are not running out of juice, you get even more (unknown) juice. It is hard to judge on paper, but when I draw into an another neutral skill and some sort of reactive event (e.g. Dodge, "I've had worse…"), I felt powerful and prepared. You'll likely get at least 1 matching icon for whatever you want to do next. It's a card that give you hope going into a fight.

In relation to other skill cards of the same series, fighting could continue and keep you susceptible to AoO for a while, contrasting to investigating or evading the enemy. The 2 draws you get felt powerful and more of a combo than bonuses, as normally you don't get more stuff to work on while fighting but rather having smaller and smaller hand. The high accuracy of can be used for one-shotting 1~2 HP weak enemy out of your clue finders with less chance of friendly fire and get some draws out of it. Or to cover everything-but- on critical Fight to finish the enemy. You can also commit to let base 3 friend without weapon to perform basic Fight to deal 1 damage accurately, though you might not get 2 draws without the weapon's boost.

For investigators who have access to Mystic (5) or Spell (5), it's hard to find a good reason to upgrade to Spectral Razor (2), Read the Signs (2) and Ethereal Slip.

A single-use event or skill must be stronger than assets that can be used multiple times to be worth including in your deck. The level 0 version of these events compare very favorably to Shrivelling (0) or Rite of Seeking (0), giving you an efficient way of dispatching with 3hp or aloof non-elite enemies, or to reach higher skill test values.

However, once you have some XP in your deck, these level 2 version compare poorly to the likes of Brand of Cthugha (4) or Rite of Seeking (4). They deal 1 less damage to elites and get 1 less clue. They're significantly more expensive than playing spell assets. They require other support cards in play before they can be used*. They can't be used multiple times per turn - if you fail a fight check you're just out of luck.

Alternative explanation using Gru's plan:

1. Set up Prophetic and Olive Mcbride (2), have Read the Signs (2) in hand.
2. Play Read the Signs for free using Prophetic, using Olive Mcbride during the skill test to guarantee a symbol draw and recur Read the Signs to your hand at the end of the round.
3. Discover 1 less clue per round than Rite of Seeking.
4. Discover 1 less clue per round than Rite of Seeking?

So, why would you take these cards? You take them because you're playing blurse and you want your arcane slots for other uses**, and/or because you don't have access to mystic 4. Kōhaku Narukami is the poster boy here, with strong economy and the being able to take advantage of the extra arcane slots.

Also, these cards are a dark horse on off-class mystics. Anyone who can take these upgraded events can also take Olive McBride, Rod of Carnamagos***, and Robes of Endless Night. Bring your own blurse generation and you have a party going.

Sister Mary gets a much needed buff with XP here, allowing her to properly flex into investigating in ways she couldn't before. She has natural symbol generation, Prophetic access, and can discount repeated plays with Rite of Sanctification. She also often runs other cards that benefit from token manipulation like Blessed Blade or .35 Winchester.

Sefina Rousseau likewise likes these events even though The Painted World doesn't interact properly with the return-to-hand effect. These events are some of the highest action-compression she can get at the time of writing, and competes very favorably with the Rogue events of the same type like Pilfer and Backstab. Rogue access also gives her cool toys like Double, Double, extra actions, the economy to support repeated plays, and lets her double-dip on the stat bonuses from Geas and The Black Fan.

//Front Daisy has better things to do in general, but can run them as a jank deck of sorts, since seeker does have good curse generation and gets acceptable mileage out of curses with Prismatic Spectacles and Gabriel Carillo.

* unless you have to discard the card after use, but why would you do that after paying 2xp for it unless you have no choice?
** e.g. for Spirit of Humanity or Close the Circle
*** despite much hand-wringing about how unintuitive the interaction is, the Rod feels obviously designed to combo with these set of cards