Me and some friends have recently got into AK in the past few months and ended up getting all the expansions. At first I just got CotDP and DH but realized it would begin to delute the threat from DH if I was to add in future expansions so I started by taking a Mythos card out for every CotDP card I put in (So if I threw in a card that openned a gate to the witch house I took one out too). But now I got them all and I decided to seperate it into two games since the amount of cards invovled was just... alot. So I divided the mythos and encounter cards as such, Orginal AK + DH + IH in one set and KH + CotDP + KiY+ DGotW.
I suspect strongly that some players were... intimated by the number of cards. We could get a group of 9 people for mtg, or dnd back in the day, we even played a 9 player game of risk 2010 before (stealing peices from other versions of risk with spare commanders) but I mention AK and we end up with 3 and sometimes maybe 4.
So I was wondering what other people do? Do they just mix it all together, or mix and match certain parts to help preserve some of the flavors (and threats!)? I guess using KH + IH could increase the threat of Aquatic monsters.
And what about item decks? I ended up going through and removing duplicate cards out to trim the size down. I tried to keep the ration of weapons to non weapons the same, or close too.

