Rating an tutor by it's minimum target just isn't correct.

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I am not rating a tutor by it's minimum target, I am taking into consideration that by Echoing Oneiromancy you draw it instead of another card and as such the value of Oneiromancy, after the Echo, is the difference in value between Oneiromancy and the card one would have drawn instead (which at the very least is a 4p card), so the Echo of Oneiromancy is, in terms of value, a relative improvement over a 4p (or more expensive) card, thus Oneiromancy being played twice takes at the very least 17 provisions into consideration.

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No it really doesn't the equivalent is what matters here.

If for example Royal degree, land of thousand fables etc. would each cost 7 provision costs they would be much closer to Oneiro.

They match more or less provision wise but have a slight advantage in draw rate being spread over 2 cards.

But still Oneirmancy still holds it's indisputable advantages: play any type of card & echo top deck.

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If those would cost 7 provisions they would be considerably more efficient than Oneiromancy, given that, as I have pointed out before, a single use of Oneiromancy is the equivalent to an 8.5p tutor (not considering the fact that the second use is only a relative improvement, rather than its full value). The Echo topdeck is mentioned in the next part.

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No this no reason to rate a card lower this could happen with any tutor

It's called RNG

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I am glad you agree.

My point was that the RNG between including 2 Royal Decree-type of cards or 1 Oneiromancy evens out, so that there is no advantage in relations to consistency I would like to attribute to one case over the other, given that they have similarly valuable advantages over each other.

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Nope this sentence is more related to Oneirmancy advantage over 10p tutors

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Again, the fair comparison would be to compare it to 2 copies of Royal Decree, which you are otherwise arguing, so I do not see the point.

Noone was arguing a single copy of Royal Decree would be equivalent.

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Nope these are not unfounded numbers like I already explained they are based on equivalents

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The statement on it having to be 10*2 = 20 provisions is out of the blue and from my perspective not consistent.

__I guess I have to put this into a more precise picture:__
1.) Your statement is not consistent under shift to an equivalent frame, if the observer moves into a different frame the consequences of your argument change dramatically.

Since deckbuilding is invariant under a shift into certain equivalent frames (like the frame of transformed provisions I was refering to above) the argument also has to be consistent in that regard.

In case of interest and context an explanation on Transformed Provisions:

1.) You take the provision cost of every card and subtract 4.

I.e. a 4p card has transformed provisions (tp) of 0, a 10p cards has 6tp.

2.) You subtract 100 provisions from the total amount of provisions you can spend for your deck, these will be refered to as available tp.

The available tp of a deck are 50 + the leader provision bonus.

3.) If you include more than 25 cards you subtract 4 tp for each card above 25 from the available tp.

(since noone really does that this step can be skipped)

Deckbuilding is exactly the same in this frame and the information you get is equivalent to a correction for the minimum amount of provisions you have to spend on each card, thus what tp show you is how you spend the additional provisions available to you.

Now if we put this into perspective (we take a 15p leader for this example, although the number does not matter).

This is easier to calculate in the frame of Transformed Provisions, however you are free to check that the results are precisely the same in the regular frame people use.

If you want to only invest your available tp (i.e. upgrade provisions) into copies of Royal Decree you can run (50+15)/6 = 10.83... copies of Royal Decree and 14.16... copies of 4p cards.

If you want to only invest your available tp (i.e. upgrade provisions) into copies of Oneiromancy you can run (50+15)/9 = 7.22... copies of Oneiromancy and 17.77... copies of 4p cards.

Since we agreed that Oneiromancy should take the spot of 2 copies of Royal Decree in the deck we can clearly see that by the statement "Oneiromancy's value, it's upsides and downsides aside, in terms of the double tutoring, is equivalent to 2 copies of similar tutors, like Royal Decree, one can include instead" we get the result that Oneiromancy is definitely quite a bit too cheap and one should only be able to include half the copies of Royal Decrees, which would be 10.83.../2 = 5.42... copies.

If we now consider the cost of 20 provisions you suggested (which translates to 16 tp) one couldn run (50+15)/16 = 4.06... copies of Oneiromancy, which would be a significant overnerf.

If we consider the 12 tp (i.e. 16 provision), I suggested would be equivalent, one couldn run (50+15)/12 = 5.42... copies of Oneiromancy.

As I have shown only for a change of the provisions to twice the tp of Royal Decree (i.e. 16 provisions) would one be able to consider running 2 copies of Royal Decree as as expensive as 1 copy of Oneiromancy.

Which would still result in a nerf by 3 provisions.