Aquila is a place that you unlock by a quest called "Aquila My friend" its based on rome, there are eagle and hipos there.
The first witchdoctor companion that you would get would be serpent augur. Serpent augur is a witchdoctor companion herself.
The second witchdoctor companion that you would get would get would be hawkules. he is a very strong hawk even know only mammals can grow muscles on there chest, but its fantasy.
The next companion you get is Zeena. Zeena is sadly not a hipo, (I would really like to have a hipo companion) but she's a bird, and birds are my most favorite things in the world are birds. she uses a bow and arow