Epitome Tagg's mother, waiting on the eighteenth floor and offered by him as a life-for-life trade.
Cornered inside Louis's chest, Epitome Tagg proposes a bargain in Warlord Chat: keep him alive and he keeps Louis alive, and his mother on the Eighteenth Floor will trade her life for his.
Princess Donut immediately objects that any such deal is impossible when the crawlers die the moment they lose. The offer establishes that Tagg's mother is present in the dungeon and considered leverage he can spend.
Tagg's hostage-currency, offered as a life-for-life exchange for his own survival.