Mina can rescue a fellow Hollower trapped in the Southern Outskirts. The rescue is a combat gauntlet through a challenging optional area; success unlocks the Hollower's Guild as a service location for the rest of the run.
FAQ
How do you unlock the Hollower's Guild?
Complete a combat gauntlet through the Southern Outskirts to rescue a fellow Hollower, which unlocks the Guild and its services (Overcentral preview).