Day 200, 12:00, for 24 hours: 540 zombies at ×41 health and ×44 attack.
Part of Endless tier 40, day 5 of 20.
When it ends:
All-Purpose Strengthener×2
Fine Sheet Metal×2
Tempered Glass
Electronic Components×2
Scrap Metal×6
Broken Glass×6
Cold Cuts
Mystery Novel (Endless rewards, tiers 30-40)