Martyr Swarm is a legendary major card out of the New mechanic pool. Spirit Seed wisps live only 12 s, but each bursts for 400% of its damage in 2 u when it fades; 6 wisps at 70% bite.

You can take it once · it only turns up when your Main 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 Hive and Colossus Wisp. Take one and the rest are gone for the run.