A battlefield on avernus, demons on the left fighting devils on the right

Devils

Loosely based on myths

In many cultures devils are just another way of saying demons, but some religions have one devil that rules all demons, but in general "devil" is a personification of evil. The word devil comes from the middle English language were it means slanderer, or to slander. In most depictions, there is one devil that rules over demons in hell, this devil has many different names throughout cultures. Some examples include: Lucifer, the angel of betrayal, Satan, Beelzebub, Mephistopheles, and so forth. Devils in mythology are usually depicted as humanoid creatures with either bat wings, curled horns, blue or red skin, or having some sort of pig or goat body parts, they are also depicted as having large burning pitchforks. In Dungeons and Dragons, the names of the devils that I listed all have a place in the realm of the nine hells as Arch-devils.

Imps are the weakest, and smallest among devils

horned devils are the mid level ranks in the infernal hierarchy

pit fiends are the most powerfull non archdevils

Asmodeus, the god of Devils

From mythology

Medieval christian devil painting by Jacob D. Backer

Depiction of Asmodeus from the Dictionare infernal

Beezlebub from the demonology