Repeating a Power means “use the Power’s text effects again”. It doesn’t grant the Elements along a card’s left-hand side again, just the text effects. The three cards with Repeat are all Major Powers. If it’s not clear how one works, just check below.

The Land Thrashes in Furious Pain: if you meet the threshold, use the Power again in a land adjacent to the original target. The adjacent land doesn’t need to have Blight in it or be within Range 2 of your Presence.

Winds of Rust and Atrophy: if you meet the threshold, use the Power again, in a land within Range 3 of one of your Sacred Sites. (This could be the original land or a new one.)

Powerstorm: grants the target Spirit the ability to use some of their played Power Cards an extra time by paying Energy. Extra uses can be on the same target or a different one. This may be used to Repeat a Slow Power Card.

In all cases, Repeats never cause further Repeats, so you can’t end up in an infinite loop.

Any changes to a power carry over to the Repeat — eg: having its Damage increased by Devouring Teeth Lurk Underfoot, or its Range / Speed boosted by Sun-Bright Whirlwind.