Xenagos Ascended can't leave the battlefield as long as a Reveler is on the battlefield.
When Xenagos Ascended leaves the battlefield, each player wins the game.

When Rollicking Throng enters the battlefield, reveal the top card of Xenagos's library and Xenagos casts that card. (This ability doesn't trigger as the game begins.)

When Ecstatic Piper enters the battlefield, Xenagos Ascended attacks this turn if able
Hero's Reward — When Ecstatic Piper leaves the battlefield, each player gains 2 life.

As long as five or more Revelers are on the battlefield, Maddened Oread attacks each turn if able.
Hero's Reward — When Maddened Oread leaves the battlefield, each player gains 3 life.

Hero's Reward — When Pheres-Band Revelers leaves the battlefield, each player draws a card.

Deathtouch
Hero's Reward — When Serpent Dancers leaves the battlefield, each player draws a card.

First strike
Hero's Reward — When Wild Maenads leaves the battlefield, each player gains 3 life.

At the beginning of combat this turn, all Revelers gain haste until end of turn and attack this combat if able.

Each player may sacrifice an artifact or enchantment. Impulsive Destruction deals 3 damage to each player who didn't sacrifice a permanent this way.

Return two cards named Ecstatic Piper from Xenagos's graveyard to the battlefield. At the beginning of combat this turn, Impulsive Return deals damage to each player equal to the number of Revelers on the battlefield.

At the beginning of combat this turn, each Reveler deals 1 damage to each player and each creature those players control.

Xenagos Ascended gains trample until end of turn and attacks this turn if able.

Xenagos's Strike deals 4 damage to each player.

Whenever a Reveler attacks, Dance of Flame deals 1 damage to each player.

As long as five or more Revelers are on the battlefield, all Revelers have haste and attack each turn if able.