Thunderstep fires when you dash. On Foxfire Relic it reads: Dashing bursts for 90% of your Power against enemies around you.

Word for word it is Dashing bursts for {value}% of your Power against enemies around you, and the number in it grows with the gear: 120 to start, 6 more for every item level.

4 bases carry it.

Awakening can reach it too — 28 spirit paths pick it up at Spirit Level 3: Hoarweft, Tempestbolt, Granitebolt, Thundercall, Flintcall and Staticedge and 22 more.