Empowered only boss drops question

This information was taken from the 0.8.3 patch notes and I added it to the CGG last patch:

There is no minimum level of corruption needed for either the third (though it is Empowered specific) or fourth boss specific drops to drop. However, their drop chance scales with the Timeline’s increased item rarity which is increased by both corruption and the enemy modifiers you have active in that Timeline prior to fighting the Timeline boss.