Toriel
Toriel is the caretaker of the Ruins and an early mentor figure in Undertale.
Role in the Ruins
Toriel teaches puzzles, SAVE stars, and the idea that fights can end without killing. Her home is a safe tutorial hub before Snowdin.
Boss encounter
The exit fight is emotional as well as mechanical. Prefer MERCY. Heavy FIGHT pressure can end the battle in ways that change later phone calls and tone.
Later appearances
Toriel returns in ending sequences depending on your route. Spare her if you want the friendliest epilogue options open.