Overcharge fires on channel tick. On a piece that carries it it reads: Beam pulses build Overcharge: +{value}% Spell Damage per stack up to {count}, fading 2 s after the beam stops.

Word for word it is Beam pulses build Overcharge: +{value}% Spell Damage per stack up to {count}, fading 2 s after the beam stops, and the number in it grows with the gear: 1 to start, 0.02 more for every item level, and it only goes off every 15 times you set it up.

0 bases carry it.