The new update is 1.4GB on PlayStation 4, and 2.1GB on Xbox One, and is available now. PC players will have to wait until April 8, though after this update PC and console updates will drop at the same time.
The patch adds the new monster variants Raging Brachydios and Furious Rajang, and new armour sets for each. These new types of Brachydios and Rajang, and the new strategies that will be needed to combat them, are discussed in the Developer Diary Volume 5 video.
As far as unlocking these tense new hunts, the patch notes say “both monsters will appear in new special assignments after finishing the main story of Iceborne and unlocking the tundra region in the Guiding Lands.”
The biggest new feature added is weapon layering, allowing item aesthetics to be customized without changing the all-important stats. You can read more about how layering works here.
The level cap for master rank armor upgrades has been raised, and a few quality-of-life changes have been made to Steamworks operations.
A new item has been added that will allow quest leaders to banish a monster from the Guiding Lands, and new decor and BGM are available for rooms in Seliana. New charms have been added, including Fury Charm V, Power Charm V, Mighty Charm III, and Challenger Charm V. All of these additions are exclusively for players with the Iceborne expansion.
The rest of the patch notes detail the various bugs that have been ironed out in the 13.00 patch–you can read through the whole list here.
GameSpot’s review of Monster Hunter World: Iceborne said, “Monster Hunter World: Iceborne is more of the same, glorious slog for everyone who’s ever been taken down by a fire-breathing facsimile of a Tyrannosaurus Rex and thought, ‘I can’t wait to do that 50 times over.'” Read the whole thing here.