- "The party is here! Work together with another player to decorate the tavern and kickoff a grand New Year of Hearthstone."
A New Year Bash (previously known as A Mammoth of a New Year) is a Tavern Brawl. It made its debut on March 29, 2017.
The fourth cooperative Tavern Brawl, this Brawl was part of a three-part series of special Tavern Brawls which celebrated the start of the Year of the Mammoth. This brawl was again released a day after the release of The Boomsday Project expansion in 2018, and again on Christmas day in 2019.
|94||March 29, 2017||April 3, 2017||Journey to Un'Goro pack reward|
|165||August 8, 2018||August 13, 2018||Brawl renamed to A New Year Bash|
|237||December 25, 2019||January 1, 2020|
|290||December 30, 2020||January 6, 2021||Decks updated for each player.|
The fourth reprisal on December 30th, 2020 gave both players a new deck. It also changed the mechanics of the brawl, making the opponent and all their minions (aside from Party Crashers and Piñata Golem) untargetable with minion attacks and harmful effects.
- An instant killing of Piñata Golem (e.g., with Poisonous minion, The Black Knight, Natalie Seline) causes the game to softlock.  
This Brawl can be described as having two stages:
- Stage 1 - Both players are able to use their Hero Power to decorate the tavern. Party Crashers begin spawning at the start of the second player's second turn, ruining the fun.
- Stage 2 - After decorating the Tavern with 25 pieces, the Piñata Golem boss appears and the players' Hero Powers are changed to Pelt. The piñata boss is able to use two abilities to destroy players' minions: Something in the Punch and Noise Complaint. Hitting the piñata will give candy cards, such as Rock Candy and Divine Sweets, to help players defeat it. After crushing and defeating the piñata, both players win the Brawl.
Player Hero Powers
|Healing Touch||2||Ticket Master||2|
|Kiri, Chosen of Elune||1||Waxadred||1|
|Forest Warden Omu||1||Earthen Ring Farseer||1|
|Cenarion Ward||2||K'thir Ritualist||2|
|Survival of the Fittest||1||Terrorguard Escapee||2|
|Neutral||Prize Vendor||2||Circus Medic||2|
|Arcane Golem||1||Twilight Drake||2|
|Dancing Swords||1||Frostwolf Warlord||1|
|Terrorguard Escapee||2||Gurubashi Berserker||1|
|Azure Drake||2||The Beast||1|
|Keymaster Alabaster||1||Keymaster Alabaster||1|
|Supreme Abyssal||2||Supreme Abyssal||2|
- Stage 1
- The starting Hero Power, Decorate, always costs all of the current player's available mana, and adds that many decorations to the shared pool of decorations. In the case that the player has 0 mana, the hero power will turn over and become unusable.
- Starting on the second player's second turn (2-mana), at the start of each player's turn, if that player has fewer than 2 Party Crashers and fewer than 7 minions, a Party Crasher is spawned for that player.
- At the end of each player's turn, all Party Crasher cards in both players' hands are automatically discarded.
- Stage 2
- The Piñata Golem boss will spawn on the side of the player who used their hero power to spawn it.
- If the boss tries to spawn or move into a player's field which has a full board of 7 minions, all of that player's minions will be destroyed by Noise Complaint. This includes Party Crashers, but the destroy effect occurs after the Party Crashers attack.
- New Party Crasher minions spawned in Stage 2 are now buffed from 3/5 to 5/7 via an enchantment called "Raucous".
- When the boss golem spawns, two Party Supplies cards are shuffled into each player's deck. There is no shuffling animation, but it can be seen that the deck sizes of each player's deck have increased by two.
- The order of events for Stage 2 is as follows:
- Player 2 Hero Powered, reaching 25 decorations. At the end of the turn, Player 2's Party Crashers attack Player 1. Then the Piñata Golem spawns on Player 2's side of the field. If Player 2's board is filled, all minions including Party Crashers are destroyed on that side. Also, if there is space on Player 1's side of the board, a 5/7 Party Crasher spawns there.
- From now on, the following repeats itself at the end of each player's turn:
- The player's Party Crashers, if any exist, will attack the other player.
- If the player's board is completely filled with 7 minions, Noise Complaint will destroy all of the player's minions.
- On the other side of the board, a 5/7 Party Crasher attempts to spawn next to the Piñata Golem. If the board is filled with 7 minions, including the Piñata Golem, no Party Crasher spawns.
- The Piñata Golem boss then moves to the opposite side of the board (to the player's side of the board).
- Finally, during this time, Something in the Punch may be cast by the Piñata Golem, dealing 2 damage to all non-Party Crasher characters.
- The Piñata Golem boss uses his ability Something in the Punch randomly, starting from the second turn after he is summoned. Note that he cannot use this ability upon being summoned. However, the ability can be used twice in a row in back-to-back turns thereafter. Also note that this area-of-effect ability damages the Piñata Golem as well.
- Like all cooperative Tavern Brawls, A New Year Bash does not use an MMR to determine matchmaking.
- Mulligan for mana ramp and any cheap minions.
- There is a limited amount of healing in both decks, so Circus Medic is not worth being corrupted in most cases. Also, since she is the best health-restoring minion in this Tavern Brawl, he is one of the best targets for spells like Sap and Shadowstep.
- The second phase can be easily ended by getting Turalyon, the Tenured or Violet Wurm after using Cenarion Ward. Turalyon will neutralize Piñata and instantly end the fight, while Violet Wurm will help in a case of the full board (see below for more details).
- The first stage can turn into an easy walk (safe preparation for Pinata) instead of constant struggle with two and more Party Crashers. To do this, it is enough to completely fill your half of the board, which will prevent the appearance of Party Crashers.
- The only difficulty is that must be done during your turn. Remove the Party Crasher with a spell and fill a free space with the minions. Druid can do it by Naturalize or Lunar Eclipse; Rogue can use Sap or Shadowstep. Mutual assistance is possible with Terrorguard Escapee or Ogremancer, if the players do not use the summoned minions for trades with Party Crashers.
- If you press Decorate and reach 25 decorations, make sure by the end of the corresponding turn, there are no more than 6 minions on your board. Otherwise, they are all will be killed by Piñata Golem.
- If Piñata Golem kills the entire board, and there was a Violet Wurm among the seven minions killed, this will cause Piñata to destroy himself, causing both players to win the fight. This may be because Piñata checks for occupancy space before checking for minions summoned from the resolution of Deathrattles, which are triggered from Piñata's Noise Complaint.
- The Piñata Golem was the first Tavern Brawl Boss to include Taunt in its card text, unlike Gearmaster Mechazod or Nefarian.
- This Brawl takes place on the Stranglethorn battlefield, decorated with party banners and stringed lights. In the third reprise of this cooperative brawl, the battlefield was not decorated.
- Before its official release, this Brawl appeared on some streamers' gameplay when they were at the Bahamas to attend the HCT Winter Championship.
- Damage inflicted by Party Crashers counts toward the "Beat Down" quest, which requires dealing 100 damage to the enemy hero.
- Some of the Tavern Brawl cards played in this Brawl count towards the quests which require playing Shaman class cards.
- For the second reprise of this cooperative brawl (named "A New Year Bash"), a death animation played on the teammate's hero when both players won the game, whereas in the first reprise (named "Mammoth of the New Year"), there was no death animation for the teammate's hero portrait.
- For the third reprise of this cooperative brawl on December 25, 2019 (the second reprise of the name "A New Year Bash"), there was no longer a death animation for the teammate's hero portrait when both players won.
- Quick Tip: Don't play Natalie in this week's Brawl, it literally breaks your game.. (2021-01-03). Reddit. Retrieved on 2021-01-03.
- This is what happens if you kill the Pinata Boss with poison!. (2021-01-02). Reddit. Retrieved on 2021-01-03.
- Ben Brode on Twitter. (2016-01-13).