I have been tested UB shadow through same months, the decklist i run is similar from josh utter leyton list, from gp las vegas. I have a very good results with it:
The list i run is:
4x delver of secrets
4x deaths shadow
4x street wraith
2x gurmag angler
4x brainstorm
4x gitaxian probe
4x stifle
4x daze
2x spell pierce
2x thoughtseize
3x fatal push
4x force of will
1x dismember
9x fetch
4x wastelands
3x watery
1x underground
1x tropical
And the aditional cards it plays are 1 sylvan library +(1-2) in the side, 4x deathrite, and (1-2) golgari charm in the side.
The sultai decklist i usually see, is the deck of an mtgo user called danker.
The list i run is:
4x delver of secrets
4x deaths shadow
4x street wraith
2x gurmag angler
4x brainstorm
4x gitaxian probe
4x stifle
4x daze
2x spell pierce
2x thoughtseize
3x fatal push
4x force of will
1x dismember
4x wastelands
4x watery grave
1x underground sea
9x fetch UB (saclding, polluted, misty, bloodstqined etc)
Sideboard:
2x engenered explosives
2x graft... Cage
2x dread of night
1x spell pierce
1x flustterstorm
4x hymn to tourach
1x nihil spellbomb
1x toxic delugue
1x submerge
This are more or less the matchup winrate:
Ux Delver 50%
4-c control 45%
(New) Miracles 40%
Dredge 60%
Otk combos 80%
Ancient tomb decks 50%
Mono black control 60%
Death & taxes 50%
Ad nauseam 65%
Shardless BUG 45%
This matchup percents are less than i have archive, because i think that i have played against bad players.