Add more alternate Medusa level variants with unique monster threats: Echo and Synesthesia. Both monsters should be equally as threatening as Medusa, with a corresponding weakness to something fairly common by late midgame (as Medusa is weak to reflection and blinded heroes).

One proposed effect (for either Echo or Synesthesia) is to be stunned or damaged by loud noises like drums. Another proposal is that noise is Echo’s strength: she is alerted by noise and turns any noise around her into damage thrown at the hero.