taultunleashed

So in the Oasis (scaled dungeon in purple lotus swamp) there is a hippo horn that you can use. After you use it, a "Hungry Hippo" runs around, and eventually comes to a stop.

Apparently you have to collect some gems to get him to become aggressive. We found a blue and a yellow one, but that wasn't enough.

Does anyone know where the others are, how many there are, or any information in getting the hippo aggressive?