This was a tough one! I ended up spending 40-odd gold to get through it- including ultimate against Helios. Thankfully Archer went down first go to Dame of Darkness, or I may well have had to spend more.
What usually works for me (like Mermaid against Stone, or Clockwork against Gold dragons), just didn't work for me this time around. And Diamond Prism was just plain nasty! All in all it was very frustrating. I just hope Archer was worth it!!!