Cataclysm fires on ultimate cast. On a piece that carries it it reads: Casting your Ultimate bursts for {value}% of your Power at enemies within 4 u.

Word for word it is Casting your Ultimate bursts for {value}% of your Power at enemies within 4 u, and the number in it grows with the gear: 200 to start, 10 more for every item level.

0 bases carry it.