League members can build a league deck used for defending their League Fortress. Starting Thursday night at 2000 server time, the league leader has a chance to select 10 Defenders and 1 Guardian, who will serve as the defense for the league that week. If the defense is properly set up, then starting Friday night at 2000, the league members will be able to attack three rival leagues, one of which is their designated Arch-Rival for the week. At the end of the week, rewards are handed out to the leagues and the ranks are adjusted based on the results.
The league ratings are determined using the Elo rating system, where a league gains or loses points depending on the relative rating of their opponent.
During the attack, you select one of your opponent leagues for that week, and then choose an enemy to fight. The fortress is laid out like a normal zone, and the battle proceeds like against any AI opponent.
- Each Defender costs 50 Energy to fight, and you gain 80 (+320) XP and 500 Bucks for defeating one. In addition, you get one Torn Mask (with a chance for a second to drop, which increases with your opponent's ELO rating).
- The Guardian (who can only be fought if all 10 Defenders are defeated) costs 100 Energy to fight, and you gain 160 (+640) XP and 1000 Bucks for victory. In addition, you get two Torn Masks and either a Silver or Gold Safe (with a higher probability of Silver than Gold).
Each opponent can only be fought once, so if you do manage to clear all three opponent League Fortresses, you'll be done for that week.
During the assault period, the scoreboard displays:
- League Clears: the number of your league members who have successfully cleared the opponent fortress
- League Defends: the number of times your league defenders have won a battle in defense
- Rival Clears: the number of your opponents who have successfully cleared your league fortress
In addition, you can view the stats for the league defenders and guardian, which features:
- League Attempts: the number of times that defender was attacked by opposing leagues
- League Defends: the number of times that defender successfully defeated an opposing attack
The league deck has substantially different limits from your regular deck. In addition, it will be played as an AI deck, with all of the advantages and disadvantages that come with that (specifically, AI decks do not use equipment, and they do not have hands, so they can never discard cards, but they have a limit of 3 plays per turn rather than 2). The limits for league decks are:
- Deck size: 75 (was originally 60)
- Attack duplication: 6
- Ally limit: 20
- Ally duplication: 6
- Event limit: 14
- Event duplication: 5
- Memento limit: 8
- Memento duplication: 1 (was originally 4)
Note that the league leader must select the 10 Defenders and 1 Guardian every week, even if nothing has changed since last week!
With the July 18, 2013 update, new "salary cap" rules were added to restrict the total power of attacking and defending decks. Each card had a given point value, with more powerful and older cards having higher costs. The full rules are detailed in the initial post here and the rule revisions here. Initially, attackers were restricted to a total cost of 1000 points and defenders to a total cost of 1500 points. In the September 12, 2013 update, Tempus cards were moved to the highest-cost tier, and the attacker limit was raised to 2000 points. The defender deck limit was increased to 75 cards to compensate, and the memento duplication limit was lowered to 1. As of December 2013, the salary cap rules were as follows:
- Genesis, Tempus, and Promo: 100 points/legendary, 50 points/epic, 20 points/rare, 0 points/uncommon or common
- Vengeance, Crisis, Rift, Villain, Tribunal, Other: 20 points/legendary, 10 points/epic, 0 points/rare, uncommon, or common
- Attacker limits: deck size of 20-75, weight of 0-2000
- Defender limits: deck size of 20-75, weight of 0-1500, maximum 1 Long Memory
As described above, you receive rewards for each enemy League Defender and Guardian defeated. In addition, at the end of the week, you will receive additional prizes depending on how your league did against its rivals. In all cases, you must have participated (at least 5 fights) in order to receive these rewards.
- vs. Archrival League:
- vs. other rival Leagues: