Echoing Equation by paying ({3} magic symbol) ({U} magic symbol) ({U} magic symbol) , causing each other creature you control to become a nonlegendary copy of
Etrata.
Deal combat damage to an opponent with
Etrata and two other creatures you control.
Etrata and the two creatures trigger.
Resolve the first
Etrata trigger, exiling a nontoken creature the opponent controls with a hit counter on it, and shuffle
Etrata into your library.
Repeat step 4 one additional time.
Resolve the last
Etrata trigger, exiling a nontoken creature the opponent controls with a hit counter on it, shuffle
Etrata into your library, and cause the opponent to lose the game.