Klaus will learn how powerful Lucien and Aurora have become in "The Originals" season 3, episode 18, titled "The Devil Comes Here and Sighs." In the episode, the Mikaelson sibling will make the mistake of underestimating the power of his clan's rivals -- a mistake that might cost him his life.

The promo for "The Originals" episode shows Klaus taunting Lucien to come out, thirsty to exact revenge on his enemy for killing Finn. Fans will remember that in episode 17, Lucien murdered Finn as he and Elijah tried to save Freya in Mystic Falls.

Lucien, hell-bent on vengeance that grew over the years, appears to be ready to hand Klaus the same fate in "The Originals" season 3, episode 18. With Aurora helping him out, Lucien becomes more dangerous and Klaus becomes helpless.

"Is this to be how the prophecy unfolds? A pathetic game of hide and seek?" Klaus calls out Lucien in "The Originals" season 3 promo. Lucien shows up from behind and puts Klaus to sleep with one big wallop.

The clip suggests that Cami is there on the scene but chose not to show herself. This gives her the chance to team up with Hayley to figure out a way to save Klaus, albeit putting herself in a "risky" risky position as the synopsis for "The Originals" season 3 episode suggests.

According to some reports, Cami's life will be in serious danger in this episode. Her precarious spot seems to be the part of the plan that makes it risky. At this point, there's no stopping Lucien so anyone who crosses them will be in deep trouble.

As for Elijah and Freya, the two will take on a powerful force in the upcoming "The Originals" season 3 episode, which could be the key to defeating Lucien for good.

Elsewhere in "The Originals" season 3, episode 18, Kol is growing more and more unpredictable by the minute after he was cursed by his ancestors. Because of this, Davina seeks the help of Marcel and Vincent to bring Kol back to normal.

"The Originals" season 3, episode 18, "The Devil Comes Here and Sighs" will air April 15 at 9 p.m. ET on The CW.