The Devils:

Devils are the true incarnation of patient evilness, tempters that corrupt the heart of mortals and constantly plot infernal schemes to bring ruin and despair into the world. From their homeland of the Nine Hells of Baator, they battle constantly against each other, ruled by the Archdevils and the most ancient of them, the now ascended devil god Asmodeus. 

Devils all adopt nightmarish appearances; they strive after men’s hearts, trading souls for power in exchange for favors and positions of authority in the infernal hierarchy. Devils possess spell-like abilities which they use to deceive and confuse their enemies, relying also on their infernal claws and weapons to slay their opponents.

Devils are not usually found in the land of the Forgotten Realms. When they are, it is because they have been summoned by an evil warlock or decadent priest hoping to establish and control a cult around them. These alliances often turn sour for the summoner. Devils almost always get the upper hand in a bargain.

Imps: 

Imps are the lowest kind of devil in the infernal hierarchy, embodying the classic image of the little horned devil. They often act as spy or pet for a higher power, advising and following spellcasters that deal with the Nine Hells. Individually they are hardly a threat for a group of adventurers, but they are cunning and vicious creatures that will not hesitate to lure Heroes of Neverwinter into a trap.

Erinyes:

As beautiful as they are deadly, the Erinyes are the fallen angels of Hell, the favorites and concubines of Asmodeus himself. Previously winged, those devils have transcended their nature with the ascension of their master, losing their wings for the power to lord over their rivals: the succubi. Deceitful creatures, even by Devil standards, their power shines brightest when tempting mortals and bargaining for souls. In battle, they lash out furiously with their sharp claws or other weapons.

Shocktroop Devil:

These imposing heavily armored devils are the soldiers and bodyguards of the infernal armies, and the ground trembles with each of their steps. They use hell-forged weapons and armor to deal death quickly to their foes. Compared to other Devils they are rather unsubtle, with a tendency for direct brutality and an insatiable bloodlust.