Mirrorball is known for effectively doubling (or tripling) the effectiveness of Magic Missile. The additional missiles fly in the same direction, with slightly different angle, effectively in the same way as Split rune of the said skill. With Split rune, only adds 1-2 more missiles, to the total of 4-5 per cast.
Stats (Level 31)Edit
"Summoned from beyond the veil of death, and disposed to send its victims back there, the malevolent intelligence within this silver sphere may only be controlled by someone with intense resolve. Once its power is harnessed, however, the ball acts as a loyal enforcer of its master's will." —Deckard Cain