Quiver Charge fires on projectile hit. On a piece that carries it it reads: Every {count}th projectile hit charges your Ultimate by {value} points.

Word for word it is Every {count}th projectile hit charges your Ultimate by {value} points, and the number in it grows with the gear: 3 to start, 0.1 more for every item level, and it only goes off every 6 times you set it up.

0 bases carry it.