I just copied something.
"But seriously, how did you do it, Doctor?" Venti asked. She had landed near them a few seconds ago but remained silent, enjoying watching Nino receive her punishment.
"Ah," Sam turned to look at the orb in his left hand then answered. "I just copied something I saw in the recordings of the previous battle."
The orb itself was a spare Valkyrie heart he had brought with him just in case. Using it he's able to create preprogrammed formations of runes, just like what he did when he discovered how to modify hearts for the first time.
"I noticed that the guy named Perseus never created a halo of his own and instead used his staff." Sam explained. "I concluded that, if he had to rely on tools to make use of the runes, anything he used most likely didn't require any mental power, which also meant I could copy it without a problem."