Overlord: Oukoku no Kan-tachi - Drama CD-tsuki Tokusou-ban
English title: Overlord: The Maid Tea Party
Japanese title: オーバーロード６ 王国の漢たち[下]【ドラマＣＤ付特装版】
Alternative titles: Overlord Picture Drama
Type: ONA
Source: Light novel
Episodes: 1
Status: Finished Airing
Aired: Jan 28, 2014
Duration: 5 min
Rating: PG-13 - Teens 13 or older
Genres: Comedy

A picture drama "trailer" released on Enterbrain's official YouTube channel, the publisher of the Overlord light novel.

It promotes the deluxe edition of the 6th light novel volume that people can purchase which has the full audio drama released on CD included. 

The drama is about the Pleiades gather together for a tea break. Here, they discuss their recent missions and their dedication to Ainz Ooal Gown.

(Source: Overlord Wiki)