You don't need to go that crazy for activating
At Any Cost ASAP. You can just put 4 copies in an already solid mono S list and go with it. We have a solid midrange plan with wonderful units and supreme removal, then we add just a bit of combo finish as dressing for memorable and fun games.
I'm very happy with running a bit of hand disruption in form of
Shakedown and
Exploit. They can be used to get rid of anything that can cause trouble including units, removal and attachments.
Cull the Deck and the nightfall effects let you turn through the deck and find what you want more quickly than you might initially expect.
Of course you can splash a secondary color to cover up shadow's weaknesses, but I'm very happy with this list as is.
I'm running a lot of very good cards as 3-offs here; I recently started running even very powerful cards as a 3-offs and only run a few cards as 4-offs, those being the centerpieces or something I can almost always happily play. I recommend you to do the same with very good cards that are situational or cost more than 4 power (run only 3 copies instead of 4). more diverse games, more options and less shiftstone to spend.
Shadow Etchings
x4
1
Shakedown
x3
1
Suffocate
x3
2
Acantha Ascending
x4
2
Annihilate
x3
2
Cull the Deck
x3
2
Defile
x3
2
Exploit
x3
3
At Any Cost
x4
3
Devouring Shadow
x3
4
Eremot, Mindsplinter
x4
4
Grand Builder
x3
4
Vara, Vengeance-Seeker
x3
5
Tasbu, the Forbidden
x3
7
Icaria, First Reaper
x3
Shadow Sigil
x14
Amethyst Waystone
x4
Rune of Illusion
x4
Shadow Symbol
x4
View Deck on Shiftstoned
Veteran mercenary is somewhat meh unless you have a lot of ways to use the card he gives you regardless of what it is (plunder/market/discard) and we dont have enough of those ways to justify him. I really wish he could let you choose one of three cards instead of giving you a random one.