Anti-Sober Cone.  The beerholder emits a 150-feet cone of booze mist from its central eye. Within that area, creatures have the Poisoned condition as they are considered drunk. In addition, each creature starting its turn within that area must succeed on a DC 18 Wisdom saving throw or waste its action toasting with a mug of beer.
At the start of each of its turns, the beerholder decides which way the cone faces and whether the cone is active.

Alcohol-based Monster. Any creature that has advantage on saving throws against the Poisoned condition has advantage on any saving throw caused by the beerholder.

Alestalks. When the beerholder takes a critical hit, it must succeed on a Constitution saving throw with a DC equal to the damage taken or lose an alestalk, and with it, lose the use of a random ale ray. After one minute, the severed alestalk regrows.

Legendary Resistance (3/Day). If the beerholder fails a saving throw, it can choose to succeed instead.

Magic Resistence. The beerholder has advantage on saving throws against spells and magical effects.

Multiattack. The beerholder can use its Boundless Revelry. It then makes an attack with its Bite, an attack with its Beer Mug and uses its ale rays.

Bite. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit:  17 (2d10+6) piercing damage plus 18 (4d8) poison damage and the target must make a DC 18 Constitution saving throw or be under the effect of a confusion spell until the end of its next turn.

Beer Mug. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit:  32 (4d12+6) bludgeoning damage.

Boundless Revelry. The beerholder summons barrels of ale and fully decked tables as it compels everone within 120 feet of it to celebrate. Each creature of the beerholder's choice within 120 feet of it must succeed on a Wisdom saving throw or have the Charmed condition.

While charmed in this way, a creature uses all its movement on its turn to dance in place and to eat and drink. While it does so, attack rolls against it have advantage and it has disadvantage on Dexterity saving throws.

An affected creature repeats the saving throw at the end of each of its turns. On a success, the effect ends, on a failure it gains a level of Exhaustion. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the beerholder's Boundless Revelry for the next 24 hours.

Ale Rays. The beerholder shoots four of the following magical ale rays at random (reroll duplicates), choosing one to four targets it can see within 120 feet of it:

• 1. Last Call Ray. The target must succeed on a DC 18 Constitution saving throw or gains the Unconscious condition as it blacks out from too much alcohol. The condition ends when the target takes damage or when another creature uses its action to wake the target.
  
• 2. Hangover Ray. The target must succeed on a DC 18 Constitution saving throw or is under the effect of a slow spell until the end of its next turn.
  
• 3. Chug-a-Lug Ray. A large mug of beer appears in the target's hand and it is compelled to empty it in one go. It must suceed on a DC 18 Constitution saving throw or gains a level of Exhaustion and wastes its action on its next turn vomitting.
• 4. Beithir Fire Ray. Hit by the strongest of all beers, the target must make a DC 18 Constitution saving throw. On a failure, it takes 36 (8d8) fire damage and 36 (8d8) acid damage and has the Stunned condition until the end of its next turn. On a success it takes half as much damage and is not stunned.
  
• 5. Armageddon Ray. The target must succeed on a DC 18 Wisdom saving throw. On a failure, it gives in to a sudden urge to start a tavern brawl - under the influence of a remarkably strong ale. It must use its reaction, if available, to move to a random creature (excluding the beerholder) and make a melee attack against it. If the attack hits, the other creature must use its reaction, if available, to strike back with an attack of its own.
  
• 6. End of History Ray. The targeted creature must succeed on a DC 18 Charisma saving throw or enter a rage, desperately wanting another mug of that particularly strong brew. A raging creature cannot concentrate, cannot cast spells and has advantage on attack rolls, however attack rolls against it have advantage too. A creature can repeat the saving throw at the end of each of its turns, ending the effect on a success.
• 7. Schorschbock 57 Ray. Hit by one of the strongest eisbock beers, the target must make a DC 18 Constitution saving throw, taking 57 cold damage on a failure or half as much on a success.
• 8. Foam Ray. The target is showered in beer foam. It must succeed on a DC 18 Dexterity saving throw or has the Blinded condition until the end of its next turn and falls prone.
• 9. Bud-Geyser Ray. The target is hit by a blast of beer - it's safe to assume that beer bottle  got shaken a lot before someone opened it. It must succeed on a DC 18 Dexterity saving throw or take 27 (6d8) bludgeoning damage, be pushed back up to 30 feet in a straight line and gain the Prone condition.
• 10. Barreling Ray. The target must succeed on a DC 18 Dexterity saving throw or be encased in a beer barrel. While in the barrel, the creature has the Restrained and Blinded conditions, cannot speak and is suffocating. The barrel is an object that can be attacked. It has 60 hit points, an AC of 14 and immunity to psychic and poison damage. If the barrel takes fire damage, it explodes violently and all creatures within 20 feet of it must make a DC 18 Dexterity saving throw, taking 28 (8d6) fire damage on a failure or half as much on a success. The creature inside the barrel automatically fails the saving throw.

The beerholder can take a total of three reactions, but only one per turn.

Reactive Toast. Trigger: A creature the beerholder can see is about to use its reaction. Effect: The creature must succeed on a DC 18 Wisdom saving throw or uses its reaction to toast with the beerholder.

Ale for Ale. Trigger: A creature scores a critical hit against the beerholder and successfully severs one of its alestalks. Effect: The beerholder immediately uses two ale rays against that creature and, if the creature is within reach, makes an attack with its Beer Mug.

Absorb Alements. Trigger: The beerholder takes force, psychic, radiant or necrotic damage. Effect: The beerholder gains resistance to the type of the triggering damage until the start of its next turn. Moreover, when it hits with a Beer Mug attack before the end of its next turn, it deals an additional 9 (2d8) damage of each type of damage it has absorbed with this reaction.

The Good Stuff (1/day). Trigger: The beerholder drops below half its HP (below 203) for the first time. Effect:  The beerholder introduces the good stuff.
It is now able to use its Legendary Actions, and immediately uses Boundless Revelry again, affecting all creatures including those that have previously succeeded on their saving throw against it.
Moreover, from now on,  whenever a creature fails its saving throw against the Anti-Sober Cone, it takes 21 (6d6) poison damage.

Once it has used its The Good Stuff reaction, the beerholder can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The beerholder regains spent legendary actions at the start of its turn.

Most Potent Brew. The beerholder immediately makes an attack with its Beer Mug and grants itself and another creature of its choice the effect of a Haste spell until the end of its next turn.

Drunkard's Joke. The beerholder tells a creature within 60 feet of it a dumb joke. The creature must succeed on a DC 18 Wisdom saving throw or take 7 (3d4) psychic damage and start laughing uncontrollably. It gains the prone condition and has disadvantage on its next d20 Test.

Drunkard's Song (costs 2 Actions). The beerholder starts a drunkard's song. All creatures within 60 feet of it and able to hear it must succeed on a DC 18 Wisdom saving throw or take 10 (3d6) psychic damage and have its movement speed halved until the end of its next turn.
If a creature fails its saving throw by 5 or more, it sings along with the beerholder, using its action or its bonus action (its choice) on its next turn to do so.