Board Thread:Episode Discussion/@comment-14138255-20161106163624/@comment-25936766-20161113012915

Salem is not omniscient, nor can she easily order any Grimm to do X. If she could, the Seer has no reason to exist.

Grimm are autonomous unless ordered. Even then, they remain autonomous besides the order. Grimm, especially older ones, don't attack randomly, they do when they are sure they can win. Ao Kuang saw a simple wooden ship with few people on board, figured it was an easy target.