Devoted Cupid appears in the second half of the first section of the Yabbashah Block in Tartarus, from floor 78 onwards. They will typically be in large groups and appear as a large shadow crawling along the floor or occasionally mixed with other shadow types in groups.
Devoted Cupid appears in the 5th though 7th Paradise in Heaven within the Midnight Channel. It will support other shadows will elemental wall spells and attack with Agidyne and Vile Assault. Upon being defeated, it may drop a Crystal of Light. Selling 10 Crystals of Light will unlock the White Feather accessory in the shop.
In Golden, it appears in the same Paradise above. It may drop Aurora Quartz for trade at Shiroku Pub.