Cause of Death:
Extreme freezing + shattering — Raziel is exposed to severe subzero temperatures and becomes fragile before ultimately shattering. This is the only way to kill him due to his specific vulnerability.
Conditions:
Happens in a situation involving low temperatures.
No regeneration, no defense — he is helpless under these conditions.
Age at Death:
He dies at age 24, young but after enough development for emotional impact.
Mental Aftermath for Sans (Post-Coma):
Trauma trigger: Cold environments, especially Snowdin, trigger memories of Raziel's death.
Psychosomatic response: Even though Sans, being a skeleton, physically can't feel cold, he mentally reacts as if he does — shivering, emotional shutdown, anxiety, etc.
Emotional distortion: He doesn't understand why he's reacting, which makes it worse. Subconscious trauma loops.