You can use witching hour to skip the firewall and abomination grand encounters (works in singleplayer, but it probably only works in multiplayer if everyone does it).

What you have to do is change the time on your device to be 3:00 AM (or close to 3:00 AM). Witching hour will always attack in about a minute or so when the time on your device hits 3:00 AM, so all you have to do is time it right.

After witching hour kills you, you can wait out the dialogue and take the free revive, which spawns you at the end of the grand encounter.

I might not be the first to find this, but I figured it's worth sharing.