Epigoni

Ebynogoi (エビノゴイ) is an artifact class magic item which allows the user to open a locked door.

Description
Ainz Ooal Gown has one such magic item in his possession and used this magic item on the treasure vault door in Feo Berkana in order to gain access to the treasure stored within.

Appearance
It looks like a piece of hand-held board.

Abilities
Ebynogoi enables the user to open doors that would require the skills equivalent to a level 90 thief.

Trivia

 * Despite its pronunciation, it's actually written as 七門の粉砕者, meaning the destroyer of seven doors which explains that it can only be used seven times.