Okkult's Invitation Secret Reward?

Hi - I’m wondering if it’s worth it to spend the time to try to beat levels III and IV of Okkult’s Invitation. Can anyone clue me in on what the “secret reward” is? Seems like a tough challenge for just two gems.

Thanks!

Secret reward is an extra 3 gems.

I can’t get past the third stage due to the cloning. Any suggestions ?

http://www.hunterislandforum.com/index.php/topic/28632-how-to-deal-with-tenebris-with-roaring-entrance/