The mechanics of Dungeon Defenders 2 are designed around the genre of an Action Tower Defense, similar to it's previous entries: Dungeon Defenders and Dungeon Defenders Eternity. The Player controls a Hero who uses Abilities and Defenses to protect Main Objectives and Sub Objectives from hordes of Enemies summoned by the Old Ones.
A Hero is one of the Defenders of Eternia who is controlled by the Player. There are 10 playable Heroes. Players can have multiple versions of the same Hero. To create a new Hero, press ESC.
The Hero Deck is a system introduced in Dungeon Defenders 2. The Hero deck soft-limits the number of Heroes a Player may bring into a combat phase to 4 and these can be hot swapped between using the function keys. In the Build Phase defenders can access all of their Heroes.
All heroes in your active deck during the combat phase receive the experience for that wave, 35% bonuses for level 50 heroes in your deck will help levelling up.
The Tavern in Dungeon Defenders 2 serves as a Hub. There are 2 Different Taverns, the Social Tavern and the Game Lobby Tavern. The Social Tavern is where a Player appears when they enter the game. The Player cannot control which instance of the Social Tavern they enter in to. From the Social Tavern a Player may speak to the War Recruiter to enter into a number of different game queues based on level and difficulty. Once a player selects a queue and clicks on the "Find Group" or "Private Game" lobby they are transferred to the Game Lobby Tavern (Unless they queue into a "Find Group" with a game already in progress).
The Tavern has a number of NPCs that the player may interact with, including Shops, Lily's Upgrade Shop, and a daily quest giver as well as a Defender's Forge and Hero Manager. The only difference in interactables in the 2 taverns is the War Recruiter and the War Table.
Maps are where the majority of game play happens in Dungeon Defenders 2. Each map is an instanced area in which a player defends specific Main Objectives and Sub Objectives from waves of Enemies. There are currently 23 maps in Dungeon Defenders 2. Maps are started from the War Table in Game Lobby Tavern.
The Defender's Forge is an old relic from Dungeon Defenders, Dungeon Defenders Eternity and the Alpha-Version of Dungeon Defenders 2. It was used to access your inventory.
The Hero Manager also doesn't exist anymore.
There are several types of accomplishments you can earn during the course of a match. For example, Feats are something earned for a particular wave of a match. Titles are something unlocked from a match that remain permanently.