The Cancel Cult

Taking massive inspiration from StartWithTheName's famous list, updated slightly with the more recent releases. Their write-up is excellent and I highly recommend it despite it being more than 2 years old.

Cycle through your deck quickly using Diana's ability, Prepared for the Worst, and Scroll of Secrets (which feels really good with the mutation) to find your Twilight Blade. Once set up, use the blade to get back what you need from the situation and keep Diana's ability drawing through your deck and blast things with big Shrivelling casts.

I would not recommend this build for a mid campaign pivot, as it is very EXP hungry.

Why not try the bless package and it's cancel cards?

The answer here is that Diana is already a character that needs her cancels to set herself up and get going, so delaying your engine to setup your setup just for slightly more efficient Dodge and Ward seems not great. Don't let that stop you from trying it out however.

Why not Empower Self?

I prefer BIGBRAINPOWER spell slinging as a playstyle choice over weapons + Empower Self, personally. I also think Empower self builds take a little longer to get going and as I said above, Diana is already a hit the ground crawling kind of character who doesn't need to be slowed down any more.

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NORMAL UPGRADES

Uncage the Soul "I've had worse…" (2) - recursive money

Defiance Counterspell - pretty much the same, but better

Holy Rosary Police Badge - fairly nice upgrade with a boost for action economy later in the game

Daring Seal of the Elder Sign - pretty strict upgrade here, nothing to say

Prepared for the Worst Backpack (2) - dig 3 extra cards and also find scrolls/badges

Charisma - so you can have Olive and initiate late and double initiate early.

"I've had worse…" (2) "I've had worse…" (5) - luxury, not needed

Arcane Initiate Arcane Initiate (3) - super luxury, unlikely to get to this point

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ARCANE RESEARCH

But don't be afraid to spend normal exp as well, especially on the early campaign upgrades. I would focus on upgrading the spell assets as quickly as possible.

Shrivelling Shrivelling (3) - extra +2 WP

Sixth Sense Sixth Sense (4) - extra +2 WP and occasional double clues

Wither Wither (4) - extra +2 WP and sometimes "damage"

Ward of Protection Ward of Protection (2) - more opportunities to use the card

Shrivelling (3) Shrivelling (5) - even bigger Shrivelling

Deny Existence Deny Existence (5) - yet another luxury upgrade if you get there