Wren can be encountered quite early, though unknowingly so. Inside the Inner Sanctum, he along with his fellow Shadow Druids Olodan and Pinta are Wild Shaped as rats. Even with Speak with Animals, they will remain silent and attempt to seem threatening.
When enough evidence of Kagha's schemes with her is revealed, Olodan and her druids will reveal themselves then openly admit to their plans. Whether Kagha is convinced or not to turn against them, he will fight to the death alongside his fellow Shadow Druids.
Assume shape of a polar bear that can Goad enemies into attacking it. The polar bear has a starting health of 30 hit points that increases every two druid levels.
While in animal shape, you can't talk or cast spells. You take on the attribution of your beast form - excluding your Intelligence, Wisdom, and Charisma scores.
When your beast form drops to 0 hit points, you revert to your normal form.