Phantom Sphere of Starbow can be mainly obtained when UR units and vision cards from the Gacha are duplicated.
Campaigns and events also give you chances to get this item.
19 Phantom Sphere of Starbows are required in total to awaken a UR unit to ★6.
9 Phantom Sphere of Starbows are required in total to limit-break a UR unit 5th times.
18 Phantom Sphere of Starbows are required in total to awaken a UR vision card 4 times.
UR Units & Tier List
Jamming Thrust
Guild Recruitment Forum
Espers Guide: Abilities, Leveling Up, Awakening
New Unit: Salire (Valentine)