The Reishicyben  

Be careful when fighting him. He can hit from far far away. My lvl 20 bard and a 23 wizzy were camping this area for exp and soon enough this guy popped. She had been waiting for him to spawn to loot something, don't remember what. Anyway we were both ready to fight the thing but then the stupid owlbear that swims around it attacked. Made things much more difficult as the bear was blue and this thing was yellow to her and red to me. I tried to take out the bear as she root-nuked the mushroom but he can hit hard and from far away. She went down quickly but got him down to about 20% health. Somehow my little bard finished both off with less than 1 red bubble left. He dropped the eye.

Two important things I have learned about him:
1. Long attack range.
2. Low magic resistance. At lvl 20, he was 4 lvls higher than me but he never once resisted BBB (my DD song).

The wizzy I was with says he is on a 2-hour timer.
Also, the Shiknars didn't add. They have a pretty small aggro range. And the mushroom is on the island in the middle of the small pool. No shiknars spawn there. The owlbear swims laps around it though.