Talk:Underworld Tower to Heaven/@comment-82.126.86.214-20170804172641/@comment-26461551-20170805045739

Well then, when you only need 1-2 runes left then you should enter the rune boss, get into a 100%-win senario, then minimise app until BP full again. Beat her and enjoy rune time with 5 BP. If you only get 1 rune, but needed 2, then just wait for next rune boss and repeat.