Hobby Japan announced the anime adaptation of Shinjiteita Nakama-tachi ni Dungeon Okuchi de Korosarekaketa ga Gift "Mugen Gacha" de Level 9999 no Nakama-tachi wo Te ni Irete Moto Party Member to Sekai ni Fukushuu & "Zamaa!" Shimasu! (Backstabbed in a Backwater Dungeon). Written by Shisui Meikyou, it debuted in 2020 on Shousetsuka ni Narou and was published by Hobby Japan in 2021. Its 10th volume launched in July, with a manga adaptation by Takafumi Oomae reaching 14 volumes this November. J-Novel Club and Seven Seas release the light novel and manga in English. Betrayed by his party, protagonist Light summons Level 9999 warriors with Unlimited Gacha, builds a kingdom, and plots revenge as a powerful Overlord.
Source: myanimelist