The Beauty in the Disastrous Rhythm

Introduction

For me, building for true solo play is about maximizing the generality of your deck and minimizing its draw uncertainty. I designed this deck to ensure you will have cards in your hand that will help you reliably respond to the largest possible set of game states and tests.

Though Diana has a very low Willpower stat (1), her special ability and Additional Setup more than make up for this weakness. She is actually a very robust and flexible investigator—as soon as you stop relying on building up her Willpower, and instead let it naturally ebb and flow throughout the game!

Note that I playtest all of my solo decks on Hard difficulty.

Getting started

Mulligan every card in your starting hand that doesn't trigger Diana's special ability, with the exception of up to one copy each of Flashlight, Drawn to the Flame, Enchanted Blade, and Physical Training. From then on, the cards in your hand should reliably support whatever actions are required of you (or allow you to forgo actions with likely strongly negative outcomes).

Note that I sometimes also mulligan Hypnotic Gaze, depending on the scenario and how likely I am to use it in the early- to mid-game. It tends to be prohibitively expensive in the early game, when I am trying to get crucial assets into play.

Once I have Crystalline Elder Sign in this deck, I typically mulligan hard for it.

General strategy

In the early-game, while her willpower is low, prioritize preventing horror using Diana's special ability. Also try to get as many assets into play as possible, while retaining 1-2 resources to make sure you can afford to play the necessary event cards.

In the mid- to late-game, while her willpower is higher, prioritize preventing damage using her special ability. Use Physical Training to boost your skill value by 1 or 2 on critical tests; only spend more resources in this way for absolutely essential tests. Ideally, you will also have Twilight Blade in play in the mid- to late-game, which will allow you to re-use crucial cards beneath Diana. Do not be reticent about doing so, as Terrible Secret will likely force you to discard them at some point, anyway.

When you do eventually draw Terrible Secret, prioritize avoiding horror over keeping cards under Diana. I typically discard every card beneath her and reset to the early-game strategy (with the added benefit of now having assets in play), unless there is a card beneath her that I know I want later on for scenario-specific reasons.

There are a large number of events in this deck, which are intended to trigger Diana's special ability as often as possible. That being said, do not be afraid to commit event cards to critical skill tests. I typically end up doing so several times in any given scenario.

Investigation

Remember that if you reduce the shroud of a location to 0 using Flashlight, then you succeed at any Investigate skill tests at that location for which you do not reveal the token.

Save Drawn to the Flame for high shroud locations, and/or locations with more than 1 clue on them. Note that this card is particularly powerful when combined with Diana's special abilities. Also remember that Drawn to the Flame does not require an Investigate action, so it can even be used to discover clues at locations that cannot be investigated!

Combat

Prioritize getting Guard Dog into play before Olive McBride (Olive McBride is primarily in this deck for horror soak and for combos with Hypnotic Gaze). Guard Dog's test-less damage and damage soak are extremely powerful, especially in the early game when Diana is still getting set up (and focusing on preventing horror rather than damage).

Enchanted Blade is the key weapon in this deck, as its gross +2 when it is "empowered" is essential for boosting Diana's combat value into a feasible range on Hard difficulty. Its +1 damage when "empowered" is also essential for action compression. Since we are not using Diana's arcane slots for anything else in this build, the fact that it takes up one such slot is of no consequence for us.

Hypnotic Gaze is included for late-game boss fights. Wait to play it until you are facing an enemy with 2 or more damage, and you also have Olive McBride in play or Dark Prophecy in your hand. Hypnotic Gaze is really only worth its 3 resource cost when you have a high probability of using its triggered ability to deal an attacking enemy's damage to itself. Both Olive McBride and Dark Prophecy substantively increase this probability, by allowing you to draw more than one token after cancelling an attack.

Taking advantage of Diana's special abilities

Remember that you can trigger Diana's special ability once per phase. This is actually quite often! Keep in mind, though, that this also means you can only place one card beneath her (and draw one concomitant resource) when you combine multiple cancellation cards together, like when you combine Hypnotic Gaze and Dark Prophecy.

When you have to choose between cards to place beneath Diana, choose the one you are most likely to play a second time using Twilight Blade. For example, suppose you have Twilight Blade in play, and two copies of Hypnotic Gaze and one copy of Dark Prophecy in your hand. You can combine Hypnotic Gaze and Dark Prophecy to cancel an attack and likely deal an enemy's damage to itself. After that, you can discard Hypnotic Gaze and place Dark Prophecy beneath Diana. This allows you to subsequently play your second copy of Hypnotic Gaze, and then exhaust Twilight Blade to play Dark Prophecy a second time and combine it with with Hypnotic Gaze once again.

Upgrades

Some recommended upgrades, in order of priority: upgraded Physical Training, upgraded Vicious Blow, Crystalline Elder Sign (replaces Holy Rosary), and upgraded Defiance.

Note that once Diana has Crystalline Elder Sign in play, she becomes an incredibly versatile investigator, with 4, 4, and 4. This makes her an extremely strong solo investigator in the mid- to late-campaign.