Garbage Monster Sludge, otherwise known as O'Sludge or Odoro is a huge black blob of black water. It is the second monster boss that Dorian has to defeat. It was created by the pollution caused by the Kingdom when oil spilled out of a container. Trees cannot grow near the sludge. Dorian tries to clean up the sludge but it is too large. Then a monster suddenly grows from the oil.
Sludge spawns mini sludge monsters. It sometimes pulls a hand to damage Dorian and his Wood Spirits. It can also explode and land somewhere else. After defeating the monster Dorian gets a Mana Crystal. He then questions how to clean the sludge up and then asks Master to do it for him later. Then he finds dirty water, and figures he has to make it clean like Taisai River. He immediately realizes that the dirty river actually connects to Taisai River, and realizing this he quickly checks that river.