Doom Eternal has got its biggest free update yet, and it is making some interesting changes to the game.
Quite notable of all is the addition of a new Horde Mode, which fans were eagerly waiting for. Along with that, there are a plethora of bug fixes and more. Here are the completepatch notes.

Doom Eternal Horde Mode Update 6.66 Patch Notes Today
Horde Mode
Compete for the highest score by battling wave after wave of demons across three Missions from DOOM Eternal and The Ancient Gods – Parts One and Two* in this challenging new single player game mode. You’ll need to keep your wits about you and your skill sharp. Like a classic arcade game, there aren’t any checkpoints, you start with just 3 extra lives - but there are more to earn as you progress. You begin with only a fully mastered Combat Shotgun, unlocking a new weapon at random as you complete each Arena Round. Earn new Milestones and unlock loads of cool new customization items as you progress!
Each Horde Mode Mission consists of the following Rounds (pictured above):

Your score is tallied at the end of each Round. You are awarded additional points for any remaining Extra Lives and BFG Ammo
Progression
You begin Horde Mode with:
Leaderboards
Rewards Galore
There are so many amazing earnable rewards in Horde Mode, that instead of listing them all via text, we thought it would be better to show you:
Stadia Enhanced Feature – State Share*
Stadia players can use State Share to save their score and weapon loadout at the end of each Horde Mode round. Use State Share to challenge your friends to beat your score or replay the round yourself to beat your own score
New Master Levels
Update 6.66 includes two new Master Levels, Mars Core and The World Spear*. Complete the corresponding campaign level to unlock each one. Access your unlocked Master Levels from the Fortress of DOOM or the Mission Select menu
BATTLEMODE 2.0
Update 6.66 brings the biggest and most important update to the game mode so far. Now, more than ever skill matters in BATTLEMODE. The more you win, the better the players you face off against will be. Complete BATTLEMODE 2.0 Series Challenges to increase your Rank, unlock new rewards and attain a higher Leaderboard position
Hot Streaks
Hot Streaks are key to the more competitive BATTLEMODE 2.0 design
The new Streak Tracker on the top of the Player Card tracks wins and losses played in Public Matches, activating after the first win as a Slayer or a Demon. When the Streak Tracker is active, additional wins are tracked ascheckmarksand losses asX’s

Additional details:
Time for some helpful infographics!
1. Streak Tracker
This is the streak tracker (not to be confused with Hot Streak) this is to highlight the user what level of streaks they are currently at. This should match up with the same state that 1A
1A. Title Card Border
The title card border surrounds the players title card, in conjunction with 1. this too shows the players current streak count and they should match the same visual style (ie: if the streak tracker is stone, the title card border should also be stone
2. Hot Streak Tracker
The hot streak counter becomes active when the user achieves 4 wins. When they do, they will complete a hot streak and win a hot streak card
A players rank will increase as they accomplish the series challenges. Below is a diagram breaking up the progress of the ranks

Hot Streak Cards
When a player completes a hot streak run, they will be awarded a hot streak card (these determine your leader board position). If you got a hot streak playing as a Demon you’ll get a Demon card. If you completed it as the Slayer, you’ll get a Slayer card
- Stone Border (Default) - 0 Win Streak(s)

2. Red Border (Hot Streak) - 1 Win Streak(s)
Streak-Based Matchmaking
With the release of Update 6.66, all Public Lobbies use Streak-based matchmaking. Streak-based matchmaking aims to match you against other players with the same number of Streak wins, broadening the match criteria over time if unmet. Players can join Public Lobbies as a Slayer, a solo Demon or as a Demon team
Series Challenges and Rank
Update 6.66 adds new Dossier pages that exclusively track your progress toward completing BATTLEMODE 2.0 Series Challenges while playing as the Slayer or as a Demon. Completing Slayer Challenges increases your Slayer Rank. Completing Demon challenges increases your Demon Rank. You are awarded a new Customization item or XP every time you attain a new Rank. Series Challenges and Rank reset with each Series changeover
BATTLEMODE 2.0 adds Slayer and Demon-based Leaderboards for each supported platform. Leaderboard position is determined by Rank attained and number of Hot Streaks completed in the current Series. Leaderboards are reset with each Series changeover
1. Cycle Type
2. Leaderboard List
Leaderboards are organized by descending order of rank
3. Rewards
Simplified Player Cards
Speaking of Rewards…
We know you just wanna see the rewards that are available right now in BATTLEMODE 2.0, so without further ado…
New Playable BALLTEMODE 2.0 Content
In addition to BATTLEMODE 2.0, Update 6.66 adds the brand-new playable Demon, the Dread Knight and new BATTLEMODE arena, Stronghold!
DREAD KNIGHT
The Dread Knight is well-suited for Demon players who have an all-or-nothing play style. With double-jump and an array of attacks, the Dread Knight is a nimble demon with and potent offensive capabilities, but the attacks require cooldowns that can leave you exposed in between use
Primary Attack: ENERGY WAVE
The Energy Wave is a Destroyer Blade-style energy projectile that yields moderate damage with a moderate rate of fire
GROUND SLAM
QUANTUM ORB
Mid-Round Upgrades
Your Energy Wave projectile reduces Berserk’s cooldown every time it hits the Slayer
Ground Slam not longer deals damage but instead creates a smoke cloud that grants temporary invisibility
New BATTLEMODE 2.0 Arena: STRONGHOLD
What better way to celebrate all that is new and exciting about BATTLEMODE 2.0 in Update 6.66 than the new Immora-inspired map, Stronghold
BATTLEMODE’s new arena: Stronghold is at the center of Hell. Acting as both a defensive position and a processing facility that helps fuel the Dark Lord’s warmachine, the environment lends itself to players who can keep moving between the different layers arena. Demon players and Slayer alike will fight over the valuable cover that the Fuel Overflow area provides. Players who master traversing between the bottom and top platforms will excel in our most competitive BATTLEMODE map to date