When do you get chillrend from the thieves guild?

In "The Elder Scrolls V: Skyrim," Chillrend is acquired during the quest "The Pursuit," which is part of the Thieves Guild storyline. You receive Chillrend after defeating the boss, Mercer Frey, in the Twilight Sepulcher. The quest becomes available after completing several other Thieves Guild missions, particularly "Dampened Spirits" and "Scoundrel's Folly."