Kyoukaisenjou no Horizon Special
Japanese title: 境界線上のホライゾン 完全新作アニメーション「境界線上のホライゾンXXI-PV」
Type: PV
Source: Light novel
Episodes: 1
Status: Finished Airing
Aired: Dec 21, 2018
Duration: 12 min
Rating: PG-13 - Teens 13 or older
Studios: Sunrise
Genres: Action, Fantasy, Sci-Fi

The Blu-ray Box set of Kyoukaisenjou no Horizon is slated to have an "all-new bonus animation." 

(Source: ANN)