
I haven't seen this mentioned, but this card would work really well with Agnes Baker. Cancel out a treachery AND trigger her ability at the same time? Great combination.
This is basically a triple Ward of Protection, but costs 1 resource and 3 health more. Obviously you can have only 2 Ward of Protection in your deck, but together with Purifying Corruption you can cancel up to 5 treacheries! This is pretty much 1/3rd of all the treacheries you will draw. Adding Agnes Baker ability, you additionally deal 5 damage while doing that. Amazing stuff.
Assuming you don't recharge the card and only cancel out treacheries three times, the full price for Purifying Corruption would be 4 resources, 3 sanity and 3 damage. The health cost especially might be a bit high for our brave waitress, but you also have access to Heirloom of Hyperborea and assuming you have more soak (which you should, if you're playing Agnes), this is definitely something she can handle.
This card also pairs extremely well with two particular allies - Peter Sylvestre and Jessica Hyde, both of whom Agnes Baker wants in her deck anyway.
The only real drawback of this card would be the fairly expensive resource cost (4), which might be a bit high for her at times, as she generally tends to be short on supplies, especially if you run her with Fire Axe or Dark Horse, which some people do.
TLDR: So overall 4 exp and 4 resource cost for a card that will help trigger Agnes Baker ability and cancel out treacheries? Definitely something to consider.
Also, if by any chance you are playing with Carolyn Fern on the team (which is a quite common duo), all the drawbacks of Purifying Corruption magically disappear.