A Devil Fruit based on Alastor from *Hazbin Hotel* could be an *Oni Oni no Mi, Model: Alastor.

Type* Zoan

Abilities*

1. *Demon Transformation* The user can transform into a demon resembling Alastor, complete with his signature antlers, sharp teeth, and other features. In this form, they gain enhanced physical abilities, like superhuman strength and speed, and possess a high degree of durability.

2. *Shadow Manipulation* Much like Alastor's control over shadows, the user can manipulate shadows to create constructs, ensnare foes, or even travel through them. This ability could also include shadow teleportation, allowing for quick, stealthy movement.

3. *Voice Control* The user can project their voice with a supernatural effect, influencing emotions and actions of those who hear it, akin to Alastor's unsettling charisma. This could be used to instill fear, confusion, or even compel people to act against their will.

4. *Hellfire* The user can conjure and control hellfire, a unique, magical flame with properties that can burn through nearly anything, including spiritual or elemental defenses.

5. *Reality Warping* In line with Alastor's reality-bending abilities, the user can make minor alterations to their environment, such as changing the appearance of objects or creating illusions, though this is less powerful than Alastor's full reality warping.

This Devil Fruit would provide a combination of offensive power, control over darkness, and manipulation, reflecting Alastor's intimidating and enigmatic nature.