Siphon fires on channel tick. On a piece that carries it it reads: Beam pulses have a {chance}% chance to feed you {value}% of the pulse as health.

Word for word it is Beam pulses have a {chance}% chance to feed you {value}% of the pulse as health, and the number in it grows with the gear: 20 to start, 1 more for every item level, at a 15% chance.

0 bases carry it.