The 27-year-old will take over as fnatic's new in-game leader, with Maikil "Golden" Selim, who had been promoted from the organisation's academy roster to guide the team, changing his role to entry-fragger.
During his second spell with fnatic, the 24-year-old helped the team to win IEM Katowice and the WESG World Finals. His final appearance for fnatic came at IEM Sydney, where the Swedes finished in 5th-6th place after losing to eventual champions FaZe.
Xizt had long been on fnatic's radar and came close to signing for them in March as a replacement for Golden. The transfer ended up not materialising as the 24-year-old was given another chance, with Xizt going on to join FaZe as Olof "olofmeister" Kajbjer had to take a leave of absence.
He returns to the organisation that he represented in 1.6 between 2010 and 2012, during which the team most notably won the IEM V European Championship Finals, DreamHack Winter 2011 and Copenhagen Games 2012.
“2018 has been full of ups-and-downs for me personally, starting with moving to a substitute role at NiP and then going on to win IEM Sydney with FaZe," Xizt told fnatic's website.
"Now, it feels good to finally rejoin Fnatic and I'm going to do my best in making us a consistent contender in the future.
"Fnatic was the organisation that helped me become a professional esports player back in 2010 and I'm really happy and proud to return to wearing the Black and Orange.
"I'd also like to thank FaZe Clan for playing there almost two months and making this transfer as smooth as possible!”
fnatic, who will make their first appearance with the new roster at the ECS Finals, from June 8-10, now have the following roster:
Jimmy "Jumpy" Berndtsson (coach)
Jonas "Lekr0" Olofsson (benched)