Please consider supporting the creator at: HiccArs https://www.hiccears.com/artist-profile.php?apid=255
Gumroad https://lvlv.gumroad.com/
Pixiv https://www.pixiv.net/en/users/127932
Twitter https://twitter.com/lvlv_art?lang=en (Im not sure where the other characters are from)
page 1-10: Male Slayer from DFO World page 11-21: Itrenok from DFO World page 22-31: Maou from The Devil Is a Part-Timer! (Hataraku Maou-sama!) (Thanks again shote1369)