343 Industries has released the April 2021 Update for Halo: The Master Chief Collection on PC. According to the team, the Steam Patch is 24GB in size, whereas the Microsoft Store Update is 50GB in size.
The April 2021 Update adds a new Halo 3 Map, the Waterfall. Waterfall is a symmetrical map that supports all major game variants in Halo 3.
Furthermore, this patch adds a new game variant, the Escalation Slayer. In this variant, players progress through a series of weapons by earning kills with each one. When a player gets a kill with the final weapon, they win the round. You can also downgrade opponents to the previous weapon tier by assassinating them or sticking them with a Plasma Grenade.
Additionally, this new patch expands the audio options and the accessibility options. Not only that, but it adds support for replacement of Halo: Combat Evolved maps with maps made for Custom Edition.
As always, both Steam and Microsoft Store will download this update the next time you launch their clients. You can also find its complete changelog here.