Iris

Appearance
From her portrait, Beel's mother seems to be a pretty woman with long black hair and gentle facial expression. She has no visible demonic features.

Personality
Very little is known about, but she seen like a very kind woman.

History
Little is known about her as of yet, other than that the she was like an older sister to Hilda, gave her her necklace and asked her to take care of Beel, and the Great Demon King once painted a portrait of her. Out of embarrassment, he created an artificial demon to stop anyone from seeing it (despite it actually being quite good). Considering that both Beel and his older brother En (who is very possibly also her son) constantly require wet nurses and Hilda mentioned that Beel probably doesn't remember her, Beel's mother might now be deceased. The Great Demon Lord instructed Hilda to become Beel's "mother", implying no one else at the time was able to fulfill that role.

Plot
Beel's mother's portrait, the "demon portrait", as it came to be known was requested by the Great Demon Lord to be retrieved by Hilda and her human companions. The painting itself was actually owned by Kugayama of St. Mark Academy, an acquaintance of Himekawa, who comments that the painting is of "a very pretty woman".

Hildegarde
Hilda used to serve Iris since before Beel was born. Iris always treated Hilda like family and gave her the necklace she is wearing in the painting before asking Hilda to take care of her baby.