Ok, so I've got a list of cards for possibilities but I'm unsure on numbers and what to mainboard/sideboard. I'm doing a rough draft with numbers and a sideboard but it'll need refining. Any and all help is appreciated.
I think declaration in stone deserves maybe 2 slots mainboard. You can cut on ultimate price. You'll want to make sure you do kill (exile) something which ultimate price wont always do if its multi color. You dont want to get ultimate price if youre playing against any eldrazi type decks. Ramp or otherwise. Alternatively, You can ditch gideons reproach for 4 declaration. That frees up 4 cards in your sideboard for hand disruption.
Maybe add 1 more avaycn as it will be huge card advantage and cut on ayli. Im pretty convinced too that any mid range should have 25 lands. Westvale abbey is definitely something to consider. You have gideon so you can make tokens. Abbey makes tokens. In mid to late game abbey is an alternate win con.
For sideboards i definitely think there should be hand disruptions like transgress the mind or even duress.
This is the list I've been having success with. Maindeck tons of removal, walkers, and 3 Languish along with Transgress for disruption, and Secure the Wastes along with Gideon and Abbey to end the game quickly. Wasteland Strangler is the only creature in the deck being very well positioned against company and weenies. Pitiless Horde comes in against decks where a quick clock is good. All of the value lands really make the deck strong late game and it can even win when badly flooded out.
Newly updated. It definitely needed Transgress the Mind to slow down CoCo and a few other decks. I hadn't played Standard since RTR rotated out so I was very unfamiliar with the current meta. I'm not a fan of Westvale Abbey, so I'm trying to avoid going that route (Setting myself up for a 6 for 1 and typically 2 turns of tempo loss due to setup the turn prior seems bad). Still looking for feedback and advice.
3 Ayli, Eternal Pilgrim
3 Drana, Liberator of Malakir
3 Kalitas, Traitor of Ghet
2 Archangel Avacyn
Walkers: 8
4 Gideon, Ally of Zendikar
2 Ob Nixilis Reignited
2 Sorin, Grim Nemesis
Removal: 16
2 Anguished Unmaking
4 Gideon's Reproach
4 Grasp of Darkness
4 Ultimate Price
2 Languish
4 Shambling Vent
4 Caves of Koilos
2 Forsaken Sactuary
8 Swamp
6 Plains
4 Surge of Righteousness
1 Languish
4 Declaration in Stone
2 Anguished Unmaking
4 Ojutai Exemplars
Maybe add 1 more avaycn as it will be huge card advantage and cut on ayli. Im pretty convinced too that any mid range should have 25 lands. Westvale abbey is definitely something to consider. You have gideon so you can make tokens. Abbey makes tokens. In mid to late game abbey is an alternate win con.
For sideboards i definitely think there should be hand disruptions like transgress the mind or even duress.
Hope you find the above to be helpful
4 Declaration in Stone
2 Ultimate Price
3 Anguished Unmaking
1 Ruinous Path
3 Read the Bones
3 Languish
3 Secure the Wastes
4 Wasteland Strangler
3 Gideon, Ally of Zendikar
3 Ob Nixilis Reignited
2 Sorin, Grim Nemesis
4 Forsaken Sanctuary
4 Caves of Koilos
1 Evolving Wilds
3 Blighted Fen
2 Westvale Abbey
4 Plains
4 Swamp
2 Duress
1 Transgress the Mind
3 Silkwrap
2 Infinite Obliteration
1 Read the Bones
2 Tragic Arrogance
4 Pitiless Horde
Modern: UW Spirits
3 Ayli, Eternal Pilgrim
3 Drana, Liberator of Malakir
3 Kalitas, Traitor of Ghet
2 Archangel Avacyn
Walkers: 4
4 Gideon, Ally of Zendikar
Instants/Sorceries: 21
3 Merciless Resolve
3 Transgress the Mind
2 Anguished Unmaking
3 Gideon's Reproach
4 Grasp of Darkness
4 Declaration in Stone
2 Languish
4 Shambling Vent
4 Caves of Koilos
2 Forsaken Sactuary
8 Swamp
6 Plains
4 Surge of Righteousness
1 Archangel Avacyn
1 Languish
1 Transgress the Mind
1 Merciless Resolve
3 Ultimate Price
2 Sorin, Grim Nemesis
2 Anguished Unmaking