I admit, this card makes me want to design a Big Hand Ursula deck. With a couple of Pathfinders, plus this, she can get all the clues, everywhere, as long as she can get 12 cards in hand, which might be a bit if an ask, but she might be up to it. Harvey or Mandy with multiple Pathfinders is a better bet, although a tad less flavorful.
Item. Relic. Tome.
You can only include this asset in your deck by upgrading it from Forbidden Tome (Untranslated), and only if "you have translated the tome" in your Campaign Log.
Exhaust Forbidden Tome: You may move to a connecting location. Discover 1 clue at your location. Reduce this ability's cost by 1 action for every 4 cards in your hand (to a minimum of ).
If you don't built a deck around this card, it's rather useless cause it takes too many actions. You should move and investigate normally and probably gain more clues, even if you 1-2x.
However if you built a deck around it, it gets really crazy! If you have 12+ cards in hand, 2 of these in play and one tome on Abigail Foreman you spend 2 actions to move 3 times and gather 3 testless clues (6 actions worth). It get's even better if you add Knowledge is Power and Farsight with events that discover clues or investigate (Extensive Research, Burning the Midnight Oil). With so much auto cluing, you may not need regular investigate actions anymore, so you don't need boosts anymore.
While all of that sounds amazing, it needs a bit of setup. You need to increase handsize limit and get to 12+ cards in hand.
- Handsize: The easiest way to increase your handsize limit is Dream-Enhancing Serum combined with myriad cards, like Astounding Revelation, Surprising Find, Segment of Onyx. If you have 9 (3 different myriad cards) of them in hand, they occupy 3 slots so you only need 3 others cards to reduce the tome's action cost to . Myriad cards also have a good chance to trigger the serum's to draw a card.
- Draw cards: Whitton Greene as another ally helps locating forbidden tomes and Celaeno Fragments. The fragments also synergise well with our deck strategy. Perception and Plan of Action allow us to discover some clues early game, while drawing more cards. Practice Makes Perfect allows 2 uses of some of these. Deep Knowledge and Preposterous Sketches draw more cards.
- Scroll of Prophecies is very efficient to draw many cards, especially with Abigail Foreman. But it limits the possible investigators to Daisy Walker and Rex Murphy who can include it (barring Versatile). Backpack 2 nearly guarantees you get the scroll in turn 1, as well as the Forbidden Tome.