Orcs Must Die! Unchained is the third entry in the Orcs Must Die! franchise presently being developed. The story is set a couple years after the events of the second game where rifts to many different worlds have opened up starting a power struggle for control over the rifts. The sides are roughly divided between the Order (aka the warmages, humans, elves, dwarves, etc) and the Unchained (the orcs, goblins, ogres, and so forth.) This split is not represented mechanically in the game however.
Like the previous games OMDU is a third person tower defense games where players can lay down traps to defeat waves of enemies, but OMDU has a competitive multiplayer focus where two teams of 5 face off on mirrored maps. To win a team must escort their minions into their opponent's rift. Each minion that enters a rift reduces that team's rift points. If the rift points reach 0 that team loses much like in the previous games.
The game has been described as a MOBA but the basic mode is more like two concurrent but opposite games of traditional OMD than it is a game of DOTA or League of Legends. Each team has lanes (amount depends on the map) to the opponents base but the lanes are independent for each team. Meaning that each teams minions do not interact with one another. Each lane has gates that the team defending that lane can open and close manually. The minions and players of the team attacking the lane will slowly break the gate if it is closed.
Players have access to a shop equivalent while in a match. They can spent coins at Weavers on various passive upgrades for the duration of a match. The Weaver screen can be brought up anywhere at any time and the effects are instantaneous. At war camps players can upgrade the level of minions spawning using leadership points and choose the type of minions to spawn. Just like the previous games minions spawn in waves. There are no break or set up periods between waves.
There are various amount of hero characters (currently 15) that players can choose from. Each with a set of basic abilities including a default weapon that has a primary and secondary attack, two active abilities that by default are bound to the "Q" and "E" buttons, as well as an innate passive ability. Players also have a hot bar that includes their traps, other abilities, and glyphs. These hot bar items can be arranged in customizable "decks" that that house cards of each equipment type (gear, traps, glyphs.) These decks are not character specific allowing characters to be very customizable. Decks are sort of like load out options of other multiplayer games but cannot be changed mid-match.
Additional noncompetitive modes have been discussed but are not implemented as of now. There are no plans for a single player campaign mode.
Closed Alpha/Beta and Founder's Packs
The game has been in a "sign up to play the alpha/beta" state since it's reveal at PAX East 2014. While the game will be free-to-play when released as of now potential players can only get into the game by buying one of the founder's bundles for instant access or by a free sign up for the chance of access. Founders gain additional starting heroes, exclusive skins, and a large amount of the paid currency, gold.