We are almost finished, but this last step is the most perilous, $N.$B$BI have the empty summoner's orb and am ready to empower it.  We will do this by harnessing the energy of a mana rift.  I'll cast a spell that will temporarily open a rift, from which creatures, mana surges, will pour out.  You must defeat the mana surges and their power will be released, which I will then collect.$B$BKill enough mana surges before the rift closes and I will place all their collected energy in your orb.