When visiting the City of Amaranthine, the Warden-Commander must talk to Colbert about the chasm he found to progress with Last of the Legion. He is standing near the entrance of the city with his elven companion, Micah. He's hostile towards a male Warden Commander and flirtatious towards a female Warden Commander.
It turns out he and Micah, fell into a pit in the Knotwood Hills and were ignored by a horde of darkspawn. He'll give the Warden-Commander the details and a map of the chasm's location. The chasm is, in fact, an entrance to the Deep Roads.
The Warden-Commander has the option of giving Colbert 1 or 10 for his effort.
After finding Micahs Lucky Charms in the Knotwood Hills, the Warden-Commander can return it to him for 250 XP by talking to Colbert. After this, both will leave.