Do Fiends Have Souls 5E?

Fiends are more or less reforged souls, yes. They also can only ever be permanently killed when on their home plane. A fiend that is killed on any other plane, just dissipates and is reformed on their home plane again. Fiends are more or less reforged souls, yes.

Do animals have souls in 5e?

All living creatures have souls. (I would be ok whit that, being a mortal body the vessel of an outer essence in the material plane) Only certain types of living creatures have souls.

What creatures have souls DND?

All living creatures appear to have a soul.

When a creature dies, its soul departs its body, leaves the Material Plane, travels through the Astral Plane, and goes to abide on the plane where the creature's deity resides.