Cross Steals the Rainbow Wing/Midnight Sparkle and the Pony of Shadows Appear/Marshadow Possess the Rainbow Wing/Midnight Sparkle Controls Tempest and Grubber/Marshadow Possess Lycanroc and all of Wild Pokemon

Here's the darkest scene

Gmerl: Now it's the time.

Samurai Jack: Go ahead, Ash, Place the Rainbow Wing to the crystal.