While the event will only be live for a limited time, it will return at a later date. Though details on that are scarce at the moment.
Here is the full overview, via Capcom:
With the conclusion of the Zorah Magdaros and Nergigante investigations, the path is now clear for the arrival of the majestic Elder Dragon Kulve Taroth.
We’ll let you investigate more details about the new Elder Dragon itself directly, but what little information the Research Commission has gathered indicates we need to deploy a new hunting strategy. Enter the Siege!
Siege is a brand new limited-time quest type which requires the collaborative efforts of all hunters in the same Gathering Hub (which can house up to 16 hunters). Each hunting party will split off into groups of up to four hunters each, but will be working together to investigate and hunt down the same 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. This new quest type is designed and balanced for multiplayer, so call up your Squadmates, or join up a dedicated Kulve Taroth lobby, and make sure to coordinate with other hunters if you want to earn the best rewards.
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. We don’t have much information on when and where Kulve Taroth has amassed all these relics, so the nature and quality of these weapons (read: type and stats) are entirely up to fate.
The Smithy, however, is already hard at work coming up with a new armor set to complement these weapons quite nicely. Be sure to pay him a visit after you’ve gathered enough Kulve Taroth materials.
The first instance of the Kulve Taroth Siege will start on April 18 at 5:00 p.m. PT / April 19 at 1:00 a.m. BST, along with our second free content update, and will be live only for a limited time. It will return at a later date, but details are very scarce at the moment, so assemble your Squad to take full advantage of this golden opportunity.
Watch a trailer below. View a set of screenshots at the gallery.