Sam (Jared Padalecki) and Dean (Jensen Ackles) Winchester continues to look for ways to open a portal to the Apocalypse World in "Supernatural" season 13. The Winchester brothers will need any help they could find in order to save Jack (Alexander Culvert) and Mary (Samantha Smith), who were trapped in the alternate dimension. Episode 15, titled "A Most Unholy Man," will see the Winchesters' effort to retrieve a special relic that will lead them to the Apocalypse World.

"Supernatural" season 13 episode 15 will show Sam and Dean working with Donatello (Keith Szarabajka) so that they could perform a ritual to open a bridge connecting the real world and the Apocalypse World. Unfortunately, the brothers would need a bunch of ingredients to make the ritual successful. However, there is one special item that they should obtain before they could go to the Apocalypse World, and that item is available only in the religious black market. According to the latest spoilers, that relic could be the grace of an archangel, something that will put the Winchesters in big trouble if they ever try to obtain it. 

Aside from going to a religious black market, Sam and Dean would also need to worry about Donatello, who is under the influence of dark magic. It is likely that the Prophet will betray the Winchesters at any time in the next episode, but the synopsis for next week does not mention about Donatello messing up the brothers' trip to the Apocalypse World.

To recap the previous episode of "Supernatural" season 13, Jack and Mary found themselves trapped and helpless inside the Apocalypse World, and the apocalyptic version of Michael (Christian Keyes) was trying to kill them. The timing of Bobby Singer's (Jim Beaver) re-appearance was just perfect, as he was able to save Jack and Mary from the fallen archangel. 

"Supernatural" season 13 episode 15 will air on March 8, 8 p.m. EST on the CW.