User blog comment:Linathan/Unit Spotlight: Heavenly Emperor Kanon/@comment-70.173.62.230-20150411051408/@comment-26140304-20150411192938

You have to use Magress's UBB last. Magress's damage reduction is a mitigation buff, which means it cannot stack with other mitigation buffs, like Darvanshel's, Shera's, Narza's, etc.

Let's say you have Darvanshel and Magress. If you use Darvanshel after Magress, you won't get Magress's mitigation buff, wasting all of the effort getting his UBB.