Endless Chorus is a legendary major card out of the New mechanic pool. Mending Chorus sings every 1.6 s at half strength with a 30% shorter buff.

You can take it once · it only turns up when your Special ability can actually use it · it can be offered for 0 of the 34 abilities.

Only one card can reshape that ability this way — this one, or Chorus of One and Warding Chorus. Take one and the rest are gone for the run.