The Winchester brothers are on their way to the Apocalyptic World, but the two will have to retrieve an important religious relic in the upcoming episode of "Supernatural" season 13. In episode 15, titled "The Most Unholy Man," Sam (Jared Padalecki) and Dean (Jensen Ackles) are going to need all the help they can get in order to open a portal leading to the apocalyptic version of the actual world. However, this will lead them to a religious black market where the required item to open the portal can be found.

"Supernatural" season 13 episode 15 will see Sam and Dean working with Donatello (Keith Szarabajka) in order to save Jack (Alexander Culvert) and Mary (Samantha Smith). The two were trapped in the Apocalyptic World, and the Winchesters need to get them out of the alternate dimension alive before time runs out. Donatello is knowledgeable about spells that could open up a rift that connects the real world and the Apocalyptic World. However, they only lack one object that will finish the spell.

With this, the Winchester brothers will find themselves in a religious black market, which is the only place that they can retrieve the important relic for the spell. Unfortunately, obtaining the religious relic will be challenging, given that the item could actually be the grace of an archangel, thus putting their lives at risk when they try to touch it.

Another problem that Sam and Dean will have to worry about is Donatello himself, which could end up betraying the brothers as he is under the influence of Asmodeus' (Jeffrey Vincent Parise) dark magic. It appears that the Prince of Hell has other plans for the Winchesters. After all, Asmodeus has his own motives for reaching the Apocalytpic World, as he wishes to use Jack against his own father, Lucifer (Mark Pellegrino).

Back in the Apocalytpic World, Jack and Mary were in trouble as the apocalypse version of Archangel Michael (Christian Keynes) tried to kill them. It is a good thing that Bobby Singer (Jim Beaver) was able to save the two from danger, thus giving them another day for the Winchesters to reach them.

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