Arcade Boss World is the new event of League of Legends that will be live from August 10 until August 24 inclusive. During the event, you will have the chance to play various missions, earn tickets from completing them and use your hard-earned tickets to craft event-exclusive loot.
To start you must first complete the mission Villains Rule! to unlock the event-exclusive New Level Icon and access to two mission lines: Game Start: Blitzcrank and Game Start: Veigar. Afterwards, missions you play require equipping specific Arcade icons to earn mission rewards. Upon completion, you will earn tickets and orbs. Tickets can be used to craft loot rewards but note that will expire from inventory on September 11. Orbs contain loot and vary in size and cost.
A special bonus reward awaits all players who will beat the levels within the time limit, by August 24.
For additional information and details, you can also visit the Official Page.