https://www.pcgamer.com/monster-hunter-world-is-getting-a-raid-style-quest-mode-and-a-new-elder-dragon/

Monster Hunter: World is getting a new limited-time quest called Siege of Kulve Taroth that will send all hunters in the same Gathering Hub—up to 16 in total—on a raid-flavored quest to track down a mighty new Elder Dragon named Kulve Taroth.   

"As each hunting party collects more tracks and breaks off more parts from attacking Kulve Taroth, they’ll contribute progress to the same Siege," Capcom explained. "The primary goal of this Siege is to repel Kulve Taroth, but its shimmering golden mantle happens to be a collection of shiny weapon relics it has gathered along its journey through the New World."