ZDaemon Thursday Night Survival #455 - Zones of Fear (Part III)

 
Travelling back to the Zones of Fear after some Akeldama break. The 3rd episode features a bit of "slaughter lite" gameplay with hordes of monsters to kill but not an overwhelming difficulty to face. If that sounds like your cup of tea, be sure to be there!
 
DMFLAGS: 1174487140 / 806496256 / 0
Skill: Ultra Violence
IWAD: doom2 or freedoom0_12_1
PWADs: zof
Maps: 21-30
Lives: 1
Players: 25/100
Item Respawn Time: 60 seconds
Player Join Limit: 5 minutes
 
Date: 30th April 2020
 
Euro session: 19:00 BST/14:00 EDT at [L@P], Finland
 
Get ZDaemon and join in.

When I tried to connect, it started to download the file zof_patch1.wad

What exactly is this file?