Sister Act: Back in the Habit

A few cycles in from her introduction, and Mary has become a much more viable primary fighter with the addition of a few key cards that bolster her meager of 3. Her access to Mystic 0-2 also helps round her out to a secondary flex spot to whatever your party needs when she's not busy smiting things. With her Holy Spear she had no problem being the primary fighter for my 3 player party, and I had a lot of fun playing her. Plus it always feels good when a teammate draws a that helps out their pulls.

The two newer level 0 cards that really strengthen Battle Mary out are:

Ancestral Token - This basically floods the chaos bag with Blesses for doing what you're already doing i.e. killing enemies. I often found the bag to be maxed out with 10 Blesses easily by mid-scenario once this is up. The fact that it is a 2 horror soak is just gravy and makes taking In the Thick of It a no-brainer.

Wolf Mask - Gives Mary free extra oomph to make sure she passes her tests.

This deck can be a bit money-hungry, but if you can get 2 or more Blesses sealed on Rite of Sanctification then you've already made more than an Emergency Cache. Sanctification is also great for sealing Bless tokens later scenario if you have a lot floating around and your Crisis of Faith hasn't popped yet and you're worried about too many Blesses being in the bag.

The key upgrades to this deck:

Holy Spear - This is her main weapon and you should be generating enough to power it. I only had 2 copies and Prepared for the Worst as the 3 "weapon" cards in my deck, and never had a problem drawing it, but you do want to mulligan hard for it. Spectral Razor and Radiant Smite can act as emergency fight options if you have a scenario where you're particularly unlucky with your draw.

Nephthys - A helpful +1 and soaks up any loose tokens for free damage or to power Holy Spear if you're short on Bless tokens and need to release Blesses to do the second Spear Fight action instead of using the testless 2 damage action. Beat Cop is kind of a trap ally and once you have other ways to boost her / reliably, you don't really need the +1 from the cops or need to double up allies with Nephthys/Cops with Charisma.

Other supporting upgrades:

Enchant Weapon - This makes the first Fight action on Mary's spear more reliable and lets you take out lesser enemies without having to worry about locking up more Blesses with the second ability. I only got one copy of it for my deck, but if you want more consistency you can buy 2.

Radiant Smite - Don't underestimate this card. For just 1 resource you can potentially do up to 4 damage. 2 of these back to back are great against the big boss of the scenario.

Luxury upgrades:

Stand Together - Kind of expensive XP cost, but can replace Emergency Cache later for money and draw.

Spectral Razor, Read the Signs, Ethereal Form - Newer upgrades that you can flex in for whatever your party is lacking. With all the bless in the bag you're likely to draw them back if you're finding you're needing multiple uses. These can be pricy to pay for in a generally money-starved deck, but if you get lucky and have a Rite of Sanctification loaded up, you'll have no problem paying for them. Or just stick with the level 0 versions.

Hallow - Just 1 is enough as an emergency for your party later on in the campaign if you find your team is cutting it close on doom.

Rite of Seeking or Read the Signs - Helpful investigate cards, but a bit expensive, especially 4 for Rite when you have other expensive assets to play. (I upgraded to Rite of Seeking but actually never got to play it in the campaign so go figure) If you're finding you need more repeated investigating power that Drawn to the Flame can't clinch for you, the level 2 Read can be a nice patch for that space. (Drawn to the Flame is strictly better than Level 0 Read the Signs since Mary can handle mostly anything that comes out of the encounter deck)

Vicious Blow - If you really need to kill things more, but Holy Spear should be enough firepower on its own.

Here's a sample final deck that was tuned to investigate as its secondary function.