Blackout

Xana William makes his appearance on Earth (along with Xana's new monsters as well as his old ones even the Creepers) which have been translated to Earth due to Xana having usage of the Translation process. While Xana William walks forward with all of Xana's monsters following him, everyone is cowering and running away.

Xana William and the monsters then stand still and there is a view of the sun that lasts for a while. Then after the view of the sun, Xana William slowly thrusts his hands forward (just like he did in that clip of him in the Season 4 preview) and starts speaking some funky language very fast as he focuses his ultimate power of levitation in moving the moon in front of the sun which forms a solar eclipse (a red eclipse actually which is when the light around the moon which appears black is red light).

After this red eclipse has been formed, some of Xana's new monsters (which have the ability to speak) speak to Xana William saying that they will cause destruction on this planet just as Xana William commands. Afterwards, all of the monsters bow down before Xana William and then depart and cause destruction while hidden in the darkness and preying upon unsuspecting victims.

Therefore, now that Xana William and the monsters are on Earth causing destruction and concealed by the darkness of the red eclipse, Team Lyoko (with their new outfits and powers) must battle Xana William and the monsters which will indeed prove to be very tough. However, this is the ultimate showdown between Team Lyoko and Xana William and Xana's monsters and Team Lyoko must prevent innocent lives from being taken by seeking out these monsters hidden amongst the darkness and also find a way of overcoming Xana William.

(SIDE NOTE: If Xana William were to perform some advanced techniques such as moving the moon in front of the sun like he did, it is required that he speak a funky language which will execute these advanced techniques. Also, you already know that in the episode "Contact," Franz Hopper took possession of Sissy who spoke a strange language. Therefore, this is sort of the same thing with Xana William except that his strange language actually makes phenominal things happen. But if he were to speak this strange language in normal language in performing certain phenominal things, it won't work. Therefore, it is required that Xana William speak in "Xana language" in making extreme things happen).