Mercia was part of Ramsey Singh's crew when they first made passing through the Devil's Shroud and into the Sea of Thieves.
Initially a sceptic about all things magical, she became a believer and studied much of the mysteries in the Sea of Thieves. She wrote her findings in many tomes detailing histories and artefacts, keeping them locked away.
Perhaps the most known thing about her is that she wore the Merfolk Earrings, enchanted jewellery that allowed the wearer to understand the Merfolk's Song.
Her fate or whereabouts are currently unknown.