Activate Woe Strider by sacrificing Iron League Steed.
When Iron League Steed dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
When Iron League Steed enters, its fabricate ability triggers, putting a +1/+1 counter on it.
Resolve the Woe Strider ability.
Repeat.
This brilliant loop hinges on the dual-faced synergy of Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, whose back face grants your nontoken creatures persist to fuel endless sacrifice. By feeding Iron League Steed to Woe Strider, the Steed immediately returns with a -1/-1 counter due to that persist grant, only for its fabricate ability to trigger upon re-entry and place a +1/+1 counter that instantly neutralizes the penalty. Because Iron League Steed enters and dies repeatedly without ever accumulating permanent counters, Woe Strider's sacrifice outlet can grind this cycle on indefinitely to scour your deck with infinite scrys.