Passive voice is less engaging than active. Writers always want the reader as engaged in the story as possible.
I changed this sentence:
Odidoddex sent out his army, and all the best animals were confiscated.
Odidoddex sent out his army and confiscated all the best animals.
The first part of the first sentence is fine. Odidoddex actively sends out the army. In the second sentence, the subject animals receive the action. If I had said the animals ran like crazy to get away, the animals would be actively running. As it is, they just stand around and get confiscated. In the second example Odidoddex is again being active. Or rather his army is, by his command.
A passive voice sentence can be used once in a while, but it is better to rearrange when possible.
A better construction for that second sentence is:
Odidoddex sent out his army to confiscate all the best animals.