Nightmares and Appalling Secrets

Just a quick note with the math for Nightmare reduction using Appalling Secrets (AS) with <a href="/wiki/No!_You_will_put_these_things_from_your_mind!" title="No! You will put these things from your mind!">No! You will put these things from your mind!</a>. The challenge has low odds of success, but compensates with a high payout in CP reduction.

Specifically, it's a luck-based 30% chance of success at getting you -10CP at a cost of 10 AS (i.e. 150 pence). Failure loses you 2 AS (30p).

Thus, the expected result is -10CP *.3 = -3CP per action, with a cost of (10AS * 0.3) + (2AS* 0.7) = 4.4AS (66p)

Generally, 5-8 actions will get you two successes and knock your Nightmares down -20CP, or from Level ~6 (i.e. (6x7)/2 = 21CP) down to Level ~1 (1 CP) for 3-4 Echoes worth of Appalling Secrets.

There's about a 9% chance of getting 2 successes after 2 actions, ~50% after 5 actions, ~85% after 10, and 99% after 20 actions. So, you'll sometimes get -10CP / A, usually around -3CP / A, almost always over -2CP / A and, in almost-but-not-quite the worst case, it's -1CP / A.