Krebskulm

Krebskulm (also known as Klem or Krum in her more peaceful form) is a major character in the anime How NOT to Summon a Demon Lord (Isekai Maou to Shoukan Shoujo no Dorei Majutsu).

She is the Demon Lord of the Soul, one of the powerful rulers among the Fallen (demonic beings) and a distant relative of the protagonist Diablo. For generations, her power was sealed within the body of the pantherian character Rem Galleu.

When released during a revival ceremony (involving some very ecchi magical energy transfer), she initially manifests in a terrifying, gigantic demonic form—but quickly shrinks into an adorable, tiny, child-like girl due to amnesia and loss of her full powers. In this cute "Klem" state, she becomes harmless, cheerful, and develops a big fondness for biscuits and sweets, while gradually forming bonds with Diablo and the group (who treat her like a little sister figure).

She represents a classic mix of "ancient terrifying demon lord" lore with the series' typical fanservice-heavy, lighthearted isekai comedy twist.