Basic:Beastmoon Monster Mayhem
Courtesy of the KingsIsle Wizard101 website:
"A little mischief and mayhem never hurt anyone...except the bad guys! Get ready to embrace your inner beast and team up with allies in an attempt to best multiple waves of monsters! Will you come out on top?
Upon entering a match, creatures are spawned across the map to fight. Defeat all those monsters to spawn a powerful boss in the middle of the map. During the boss fight, Artemis will place some additional monsters outside the Spiral battle which unlock buffs for the players in the boss battle when defeated! If you succeed in defeating the first boss in the time allotted, you’ll move onto the second wave. If you can quickly make your way through three waves of monsters and bosses, you’ll win the whole event!
Unlike the Beastmoon Hunt, Beastmoon Monster Mayhem is a PvE event – meaning that you won’t be playing against other players. Instead, your enemy is the clock and waves and waves of monsters!"
Entering the Beastmoon Monster Mayhem Event
To enter the Beastmoon Monster Mayhem event, Wizards must click the special event icon next to their friends list, then select the event banner to join a match. Clicking "Join Match" will add Wizards to a matchmaking queue until a lobby fills up, where they will then be able to teleport to the Beastmoon Battlegrounds when they're ready.
Wizards will be taken to the Beasthall inside of the Battlegrounds. There will be a brief preparatory period where Wizards can choose their Beast Form and load their deck with Battle Cards until the timer runs out and the Battlegrounds open.
Inside of the Monster Mayhem Battlegrounds, Wizards will face waves of enemy monsters and must team up to defeat them as quickly as possible before time runs out. Defeating these monsters grants the victors a small amount of loot, and defeating all of the lesser monsters will unlock the Boss monster at the center of the map. Once the Boss appears, more waves of monsters will appear around the edges of the Battlegrounds; while part of the team takes on the Boss, others will take on the lesser monsters. Wizards that take on the lesser enemies around the map can win bonuses for their allies at the center who are taking on the Boss, making it easier for them to be taken down. If the Boss is defeated before the time runs out, then all Wizards will receive rewards and be sent back to the Beasthall where they can prepare for the next Stage.
Each match consists of a maximum of three Stages, with each progressive Stage becoming more difficult but offering better rewards. Wizards win the match if they are able to make it to the third and final Stage and defeat the Boss. However, if Wizards are unable to defeat the Boss at any Stage before the timer runs out, then the match ends.
The Battlegrounds for Monster Mayhem subject Wizards to the same rules that are applied across all kinds of Beastmoon events (see more details here).
Three groups of 2 enemies will appear at different Battle Rings around the map, and Wizards will need to split up and defeat all of the present monsters. Certain Battle Rings will only spawn enemies during certain Stages. There are four Battle Rings from which enemies can appear from, which are labelled in the diagram below. Once all enemies have been defeated, additional teleporters will open up around the Battlegrounds that will take Wizards to the Spiral Battle Ring, the Battle Ring found at the center of the map that houses each Stage's Boss enemy, who has a number of Minions equal to the Stage number. While some of the team takes on the Boss and their Minions, the rest of the team can go back out into the Battlegrounds at take on newly-spawned enemies both at Battle Rings and other areas to supply the team at the Spiral Battle Ring with special "Ring Spells" (see more below), which will grant them an advantage against the Boss.
1: Star Battle Ring
At the beginning of the first Stage, enemies will appear at the Star , Moon , and Sun  Battle Rings. Enemies will occupy the Moon, Sun, and Eye  Battle Rings at the beginning of the second Stage. At the start of the third Stage, enemies will appear at the Star, Sun, and Eye Battle Rings. Only the Boss monster and their Minion(s) for each Stage appears at the Spiral  Battle Ring. The additional Battle Rings [6-9] host Monsters that appear once the Boss is unlocked, each of which offers a different Ring Spell to be obtained.
Once Wizards are transported to the Beasthall, they are given 60 seconds to prepare where they can select their Beast Form, purchase Battle Cards from Actaeon, and discuss strategy. Once the 60 seconds have expired, a timer is initiated with 10 minutes on the clock. Wizards must clear Stage 1 before this timer expires, otherwise they will lose the match. If the Boss in the Spiral Battle Ring is defeated before the timer runs out, then 12 additional minutes are added to the clock, which stack onto however much time Wizards had left. If the Stage 2's Boss is defeated, then 14 minutes will be added to the clock, again stacking with whatever time was leftover from Stage 2. Wizards can see how much time is left in the match by viewing the timer at the top of their screen.
Clams, Chests, and Clocks
Around the Battlegrounds, Wizards may find various objects that they can interact with. In the Celestia Battlegrounds these are pink-colored Clams, while in the Avalon and Mirage Battlegrounds these are golden chests and mechanical clock flowers. These chests and the majority of these Clams, which are called "Coin Clams", will grant the Wizard who opens them anywhere from 10-20 Coins . Chests and Coin Clams show up in a limited but plentiful amount around the Battlegrounds, and a new batch will appear at the beginning of each Stage. However, another rarer kind of object, either the Clock Father or the Time Clam, will grant an additional 2 minutes to complete the Stage should a Wizard find and open it. Only one of these can appear per Stage, but they will not be present at the beginning. After about a third of the Stage's time has run out, the announcements, "Pay your respects to the Clock Father!" or "Time Clam Cometh!" will be made to all Wizards, letting them know that these can now be found.
Coin Clams and Time Clams are similar in appearance, and can only be differentiated by getting near the Clam and checking their overhead name.
Ring Spells are rewards for defeating monsters outside of the Spiral Battle Ring after the Boss monster appears. Once the Spiral Battle Ring is unlocked and monsters return to the Hunting Grounds, Wizards who are not engaged in combat with the Stage's Boss may duel against lesser monsters to unlock these single-use Spells to assist their teammates at the Spiral Battle Ring. The Ring Spell that each monster grants will be shown as a translucent, floating image next to the monster that defends it so that Wizards know which Spell they will be unlocking.
If a Wizard defeats the monster that is guarding a Ring Spell, then that Spell will be cast in the Spiral Battle Ring at the beginning of the Round after the Ring Spell is acquired. Artemis New Moon will choose a Wizard at random to cast the Ring Spell at no Pip cost, and it will be interrupt-cast before any other Wizards' or monsters' turns. Ring Spells' effects can vary from adding Absorption Wards or Blades to the entire team, to dealing Damage to all monsters in the Spiral Battle Ring! Wizards not participating in combat in the Spiral Battle Ring must carefully choose which Ring Spells those at the Spiral Battle Ring will need, and communication is required to optimize their effects.
Rewards are received upon defeating monsters and the completion of each Stage. Defeating monsters outside of the Spiral Battle Ring will award Rune Reagents, which are helpful in Deckathalon Events, and small amounts of Gold. Defeating Boss monsters and completing each Stage grants even better rewards, including those previously mentioned, Lunari, Thread Reagents, Moonstone Reagents, and Moongold Dust.