As the description says this is unlocked by surviving until the 31st minute in the Mad Forest level. If you start this in Endless Mode death doesn't appear and you will be able to get to the 31st minute with no problem which may unlock this. If you don't have access to that then the following is the method I used.
Set UpFirst of all you will need to unlock the Randomazzo:
I also used the Arcana IV: Awake card which is unlocked by getting Krochi to level 50.
Running Through The LevelMy approach was to do this with the Arcanas option enabled for the level and select the Arcana IV: Awake card before starting my run. This gives you +3 revivals.
After starting the run my main priority was to equip Clock Lancet and Laurel. Clock Lancet freezes enemies in a clockwise pattern and Laurel shields you from damage. You could also look for the Tiragisú item which can give you two more revives.
All you need to do then is ensure you have enough damage / healing to get to 30 minutes. This will vary for each player as we all have our preferred builds.
As soon as the clock ticks over 30 minutes all enemies will vanish and the reaper will start chasing you. Pick a direction and run. The idea is that the Clock Lancet will freeze the reapers (hopefully before they get to you) and the Laurel will protect you for a while if they do. If/when you die just revive and start running again.
I found that the Clock Lancet worked so well that once I'd passed 31 minutes I'd have to stand and wait for up to another minute for the reapers to kill me.