My wife, Mercia was "diagnosed" by the Medical section as having some sort of disease they wouldn't identify. She's dead now, and those sons-of-bitches won't even tell me why.”— Daniel Koster
Mercia Koster was one of only six residents in the vault to die from something other than the experiments themselves. According to the Vault 87 terminal entries, she died of natural causes due to cancer type 1 categories.
Mercia Koster is mentioned only in Fallout 3.