Echidna is the Witch of Greed from Re:Zero, known for her insatiable thirst for knowledge, claiming to embody her desire for wisdom even after death. She resides in a spirit world called the tea party within a tomb, where she invites Subaru, blocking the Witch of Jealousy. Initially appearing wise and considerate, her true nature reveals an infinite egoist who views everything as a tool for her curiosity. She is upright about her promises regarding lying, approaches Subaru amicably, offers help, and attempts contracts while being aware of his Return by Death ability.