Shinjiteita Nakamatachi ni Dungeon Okuchi de Korosarekaketa ga Gift "Mugen Gacha" de Level 9999 no Nakamatachi wo Te ni Irete Moto Party Member to Sekai ni Fukushuu & "Zamaa!" Shimasu!

When Light is kicked out of the Concord of the Tribes, his former comrades instantly turn on him. Light escapes this diabolical act of betrayal by the skin of his teeth...only to find himself in the deepest part of the Abyss, the most dangerous dungeon in the realm! To avoid being eaten by carnivorous monsters, he uses the Unlimited Gacha, his sole magical skill. But where it previously only produced junk items, this time Mei—a gorgeous Level 9999 fighter in a maid outfit—springs forth! Fast forward three years and Light has carved out his own kingdom in this backwater dungeon, summoning more beautiful Level 9999 warriors who swear absolute fealty to him. Now a powerful Level 9999 Overlord himself, Light plans to ascend to the surface and take revenge on his betrayers one by one!

(Source: J-Novel Club)