Untap, upkeep, Draw, Swamp, attack with Szadek (if successful, you mill 20 cards), Done.
Spiderman: 14
Hand: 2
Library: 41
In Play:
(U,U) Underground River (B/U Pain land)
(U,U) Watery Grave x2 (B/U Ravnica Dual)
(U,U) Island x2
(U,U,U) Swamp x3
(T) Szadek-Lord of Secrets (40/40?, flying, if...