Update (Sept. 29): You can now permanently unlock Collei for free just by completing Floor 4, Chamber 3 of Spiral Abyss once, as of patch 3.1. The post below is based on a limited-time event that ran in patch 3.0.
Genshin Impact’s new four-star Dendro character, Collei, is available for free for a limited time through the “Graven Innocence” event. She’s featured in Tighnari and Zhongli’s banner as a rate-up four-star character, but if you don’t want to spend your precious Primogems to get her, you can nab her for free.
To unlock Collei, you need to be at least Adventure Rank 20, and you must complete parts of the event quest, “The Unappreciated Carving.” You’ll receive Collei before the quest is complete.
If you enjoy the story, you should complete the Archon Quests up to “The Trail of the God of Wisdom” before starting the event, as the game recommends. It took us about an hour and a half to complete “The Trail of the God of Wisdom” at a brisk pace. The event can also be accessed through “Quick Start” in the event page after finishing the Archon Quest “Prologue: Act I - The Outlander Who Caught the Wind.”
Collei is a four-star Dendro bow-user who is available for free during the “Graven Innocence” event. She will be useful for any puzzles that require Dendro around Sumeru.