Mirror Ward fires on ward granted. On a piece that carries it it reads: Wards you grant reflect {value}% of the damage they absorb at the attacker for 10 s.

Word for word it is Wards you grant reflect {value}% of the damage they absorb at the attacker for 10 s, and the number in it grows with the gear: 20 to start, 1 more for every item level.

0 bases carry it.