Er wordt een belangrijke ontdekking gedaan wanneer een Egyptisch document uit de elfde eeuw teruggevonden wordt. Deze leidt op zijn beurt naar de plek waar de kelk van Het Laatste Avondmaal zich bevindt. De zoektocht overbrugt enkele eeuwen en beslaat tevens gebeurtenissen die beschavingen wereldwijd hebben gevormd.
Nee, helaas is Onyx: Kings of the Grail nog niet beschikbaar op Netflix in Nederland.
| Directing | Roberto Girault | Director |
| Crew | Valentín Diez Morodo | Thanks |
| Directing | Daniel M. Caneiro | Script Supervisor |
| Writing | Margarita Torres | Writer |
| Art | Itziar Sagasti | Production Design |
| Costume & Make-Up | Alicia López | Hair Department Head |
| Crew | Mabel Villagra | Technical Advisor |
| Lighting | Raúl Pavón | Gaffer |
| Camera | Jorge Casabán | Key Grip |
| Camera | Marco Mastropietro | Still Photographer |
| Production | Pedro Palacios | Executive Producer |
| Camera | Rafael Bolaños | Director of Photography |
| Sound | Eduardo Ortega | Original Music Composer |
| Editing | Adoración G. Elipe | Editor |
| Production | Óscar Cifuentes | Producer |
| Writing | Luis Reneo | Writer |
| Sound | José Luis Alcaine Bartolomé | Sound Designer |
| Crew | Miguel Olarieta | Special Effects |
| Production | Óscar Cifuentes | Executive Producer |
| Writing | Roberto Girault | Writer |
| Production | José Jaime Linares | Production Director |
| Costume & Make-Up | Giovanna Ribes | Costume Designer |
| Sound | Carlos Lidón | Sound Recordist |
| Production | Carla Hool | Casting Director |
| Costume & Make-Up | Sonia de la Fuente | Makeup Department Head |
| Directing | Luis Reneo | Second Unit Director |
| Directing | Chris Downs | Second Assistant Director |
| Directing | Patricia Ordás | First Assistant Director |
| Sound | Miguel Ángel Caprara | Foley Artist |
| Writing | Margarita Torres | Book |
| Writing | José Miguel Ortega | Book |
| Production | Eduardo Lis | Production Manager |
| Visual Effects | Helmuth Barnert | Visual Effects Supervisor |
