Double Rally is a legendary major card out of the New mechanic pool. Grand Convergence rallies twice, 0.3 s apart, at 70% base; the cooldown is 60% longer.

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 Implosion and Far Convergence. Take one and the rest are gone for the run.