It really depends on your purpose for entering. Yes leaving the nadir dumps a lot of nightmares and can be used in that way, but it is a -very- expensive method considering it costs stats and wastes your card slots while in the nadir. There are much better alternatives for nightmares reduction out there in london proper.

Ideally you are entering the nadir to grind a specific resource or card. Nightmares cards bloat the deck by adding a huge amount of menacing or non-profitable cards thus making the odds of drawing specific grind cards [spoiler]such as the end of battles (best card) or an unlikely garden (enigma grind) or Do you remember how they came to that place? (end game rubbery grind) or even A weakness in the air (dreams grinding)[/spoiler] highly unlikely. If you go into the nadir and all you get is nightmare after nightmare and nothing else, you've just wasted dozens of actions on a few cp of nightmares.

Each point of irrigo eats 5 cp of stats across all four stats. Even difficult challenges only give you 3 or four cp. So for example an irrigo of 9 would take 9x5x4 cp away from you or 180 overall. Divide that by 3 and you've just spent 60 actions. Now compare that to say, the nightmare confession which reduces 7-17 cp of nightmares an action. at Nightmares 9 you have no more than 45 cp total nightmares. At its worst 7 cp reduction you'd 0 out the nightmares in about 7 actions. Even considering an additional 7 actions to grind up sudden insights, 14 actions is substantially less than -60- actions (also at its best 17 cp reduction you spend 3 actions and 3 for insights ie 1/10th of 60). And you get the bonus of getting better odds of profit while in the nadir. This is just one example, and one method of nightmares reduction, but I hope it helps to clarify why its common practice to 0 nightmares before entering the nadir.

I suppose if you had no intention of grinding in the nadir and just left as soon as possible, the efficiency of the nightmares reduction would increase. Leaving at Irrigo 5 or less is only 1 cp x4 stats per irrigo. A maximum of 5x1x4 or 20 cp at irrigo 5 is like 6 actions which is comparable to the social action at its best. The efficiency of Nadir's nightmare reduction also decreases if you enter with less than maximum nightmares. For example, if you enter with nightmares 1 that basically takes a single action to removed when not in london (or a goldfish), but in the nadir its enough to bloat the deck and give all the same drawbacks as higher menace.

Note the numbers above assume that leaving the nadir sets nightmares to 0, but it doesn't actually do that. Or at least it didn't last time I checked. It would just give a reduction at less than 5 irrigo and at 6 or more irrigo it would set to 1. But that might be outdated information since I haven't been back in a few months. Can anyone confirm the reduction mechanics of modern irrigo? Does it set nightmares to 0 or halve them or just reduce a large amount of cp? This would be good information to have.

edited by NiteBrite on 11/30/2014