Ancient Tongues from the Elder Scrolls arrived at the Naruto/Boruto verse. They went there because Vaermina sent them there, and they are tasked at killing the Legendary Team 7 (Hokage Naruto, EoS Sasuke, adult Sakura Haruno)
Ancient Tongues are Gormlaith Golden-Hilt, Felldir the Old, and Hakon One-Eye who clashed with Alduin and banished him to the future.
All sides are bloodthirsty
No one has knowledge of each other
Vaermina only spectates, and can't intervene.
The Ancient Tongues bring an Elder Scroll with them.
The event in Naruto/Boruto occurs after Boruto and Kawaki rescued Naruto from Jigen's dimension.