Series 3: Recon

Season 3: Recon is the third season implemented into Halo: The Master Chief Collection. The Season debuted on September 22, 2020, with the launch of Halo 3: ODST as part of the collection on Steam and Windows. Although launched alongside Halo 3: ODST, the cosmetic unlocks available focus on adding new skins for Halo 3's multiplayer alongside new nameplates and Firefight characters. This season was preceded by Season 2: Spark.

Seasonal events and challenges
Season 3 saw a new wave of Seasonal Challenges added for completion, with three offering the unlock of four exclusive Firefight characters not available in the original Halo 3: ODST or the Season 3 unlock table - these being the Bug-Splattered Buck and Injured Romeo skins (helmeted and helmetless), respectively. A number of other season challenges are also available to earn and XP.

Season unlocks
The seasonal unlocks for Season 3: Recon take the form of the skins for weapons and visors in the multiplayer of Halo 3, Firefight character unlocks for ODST and ODST-themed nameplates for use in the menus. For The Master Chief Collection, the unlocks have been divided into 5 tiers of ten unlocks each. To progress a tier, all ten unlocks within must be unlocked. The season features over 80 unlockables, a departure from the 100 tiers seen in Seasons 1 and 2 due to the much shorter development time between releases. Including Challenge unlocks, Season 3 introduces to The Master Chief Collection;
 * 12 Halo 3 Weapon Skins.
 * 30 Halo 3 Visor Skins.
 * 10 ODST Character Skins.
 * 4 ODST Character Skins (Unlockable via Challenges).
 * 30 Nameplates.

Each unlock slot can be unlocked for - or  for Firefight characters - rewarded through the collection's updated rank scheme or the Challenges implemented in the prior Spark update. In total, are needed to unlock all content in Season 3.

Patch notes
Season 3 launched alongside a large patch for The Master Chief Collection, with bug fixes and quality of life changes. The patch notes can be seen in full below.

New Features

 * ODST is now available on PC!
 * ODST Firefight has been added to Xbox, Steam, and Windows Store, included with the ODST DLC package.
 * ODST Firefight now supports custom game variant options for creating your own Firefight modes.
 * Season 3 has been added to the collection, featuring ODST Firefight Customization, New Halo 3 Weapon and Visor Skins, and new nameplates including:
 * 12 Halo 3 Weapon Skins.
 * 30 Halo 3 Visor Skins.
 * 10 ODST Character Skins.
 * 4 ODST Character Skins (Unlockable via Challenges).
 * 30 Nameplates.
 * A new frontend menu has been added to welcome ODST Firefight Customization to the collection.
 * Halo 2 Anniversary Multiplayer’s Customization has been broken down into per-part pieces.
 * Added Challenges to the Pause Menu for visibility during gameplay.
 * Added an option that allows users to disable the Challenge notification.
 * Added deck progress counter in Challenge Hub.
 * Progress notifications for featured (golden) challenges now appear gold.
 * More variety is present for Challenges which reward Season Points from week to week.
 * Added ODST's Silenced SMG, Automag, and Brute Plasma Rifle to Halo 3 Multiplayer.
 * Added Recon weapon set to override all weapons on the map with their ODST counterparts.
 * Added new option for Halo 3 Grenade Regeneration which includes Firebomb grenades.
 * Added bottomless clip option for Halo 3 Infinite Ammo setting.
 * Simplified Chinese Text Language is now supported in ODST.
 * Flight Improvements Brought into MCC Retail

These improvements came from feedback reported by our community and were resolved during or after the flight period of ODST. Thank you for participating!

Halo 3

 * We have brought over the improvements made in our last flight patch to hit registration in multiplayer (related to the 60hz and 30hz engine refresh rate as referenced in our development July 2020 blog).
 * Fixed several issues that caused floating turrets, mongoose falling from the sky, and a series of issues that were identified during the initial flight with Elephants on Sandtrap.
 * Service ID's shorter than 3 characters now  display  in gameplay.
 * Scoreboard player scrolling is now bound to Up and Down arrow keys.
 * Updated how the camera intersects with objects in Forge fixing an issue where players would be flung out of the map boundaries and killed when playing or moving objects.
 * Several improvements to Forge with camera movement, menu navigation, and placing or moving objects.
 * Halo 3 matchmaking game films no longer prevent players from restarting the film.

Halo 3: ODST

 * Fixed an issue that caused missing or delayed subtitles during cutscenes.
 * Detached turrets no longer use lowered crosshairs when Crosshair Position is set to “Centered”.
 * Players can operate and exit hijacked Ghosts without others seeing them as standing on it.
 * Resolved several crash issues reported during the flight period.
 * All the character models have matching hands.
 * AA Wraith Spawns normally in “Lost Platoon.”
 * Suicide Grunts now have grenades in their hands.
 * Projectiles are visible when Wraiths are seen firing.
 * Players can use health packs in Firefight. Scope zoom sound effects only play once in Firefight.
 * When the time limit expires the game ends instead of a new game starting before the end of the current game in Firefight.
 * Front turrets on Phantoms are visible to players in Firefight
 * The preview images were corrected for several reward tiers (Romeo and Buck, Helmets on/off).

Resolved Issues
Below is a breakdown of the specific fixes that have come with today’s update:

General/UI

 * Exit Experience no longer plays sound effects for 0 Challenge XP.
 * Post-game and pause menu roster no longer display player names as “Player Found”.
 * The Refresh Pings button no longer disappears if user passes over Relays option after viewing Network pings.
 * Players will no longer get a duplicate notification of the same challenge when progress is made.
 * The player emblem is no longer missing the background image for all users that appear in the pause menu roster.
 * "Playlist stats" is no longer missing "Max local players" in the "Competitive" game mode selection menu.
 * The warning when enabling a zero-scoring skull has been updated to define that any "mission completion, scoring, time, Challenges, and par achievements will not be recorded when running campaign with a zero-scoring skull.

Halo: Combat Evolved

 * The customization menu "Schism" skin texture placement is no longer inconsistent with other Fuel Rod skin textures.
 * The preview model will no longer show the last visor color highlighted when highlighting “DEFAULT” instead of the default color.

Halo 2 & Halo 2 Anniversary Multiplayer

 * Armor descriptions are no longer missing from Spartan Armor Customization.
 * In Halo 2 Anniversary Forge, hovering over a different highlightable field before selecting "Yes" on a prompt no longer causes the action to not be taken.
 * Crosshair no longer moves up when zooming if crosshair position is lowered.
 * The Edit Mode action "Grab Object" is no longer assigned to a random key every time the game is restarted.

Halo 3

 * Crosshair no longer moves up when zooming if crosshair position is lowered.
 * The prompt no longer indicates [Q] (instead of assigned key) to enter edit mode at the beginning of the forge session.
 * Boot Player prompt no longer contains references to the Xbox One console on PC.
 * Objects placed when nearing the total object limit are now saved.
 * Objects no longer despawn when too many are placed on maps with high object density.
 * Changing to Player Mode while moving an object set to phased physics no longer causes the object to continue moving indefinitely.
 * Forge object rotation is more responsive with a mouse when using an unlimited framerate.
 * Objects set to fixed or phased physics no longer maintain momentum when released and changed to normal physics.
 * Players and held objects are no longer rapidly accelerated when cameras and objects are misaligned.
 * The callout to Summary now reflects actual key binding.
 * The picture-in-picture display in the Sniper Rifle's Scope will now appropriately reflect the player’s view when the crosshair is centered in Halo 3.
 * The progress bar in Halo 3 Theater is now filled during playback. All weapons, vehicles, and grenades now appear in the appropriate kills category in the Post Game Carnage Report.
 * Halo 3 armor components now display description strings in the Customization menu.

Halo 3: ODST

 * Look Inversion set to Inverted no longer overrides Flight Inversion while in Banshee while using Controller.
 * Updated the Epilogue thumbnail & loading screen image to remove a spoiler.
 * Excessive flashing no longer occurs in security camera shots in cutscenes in 4K resolution.
 * Tools of Destruction no longer displays the Halo 3 Magnum instead of ODST Magnum.
 * Suppressed SMG tool of destruction is no longer displayed as standard SMG.
 * There is no longer a large visible gap in the center of the Health Bar in 4K resolution.
 * Com Data UI no longer consistently blinks while viewing any Com Data.
 * Weapon icons in gameplay have been updated to higher-quality versions.
 * Fixed an issue where the VISR's intel menu did not display objectives as individual bullet points.
 * There is no longer a misplaced period for weapon pickup text in Italian.
 * Betrayed ODSTs no longer appear as Spartans in the Post Game Carnage Report.

Halo 4

 * Friendly Fire has been disabled in various Halo 4 Big Team Battle game variants, most notably in Team Heavies.

Halo: Reach

 * Engineer is no longer listed as Huragok in the Post Game Carnage Report for ODST and Halo: Reach campaigns.
 * Firefight Matchmaking now gracefully prompts a User without the DLC Entitlement or Campaign Content.
 * Crosshairs no longer move up when zooming if crosshair position is lowered.
 * The picture-in-picture display on Covenant vehicle dashboards will now appropriately reflect the player’s view when the crosshair is centered.