League Achievements are optional challenges that require the combined efforts of all members within a League. Upon completion of each Achievement, a League will be rewarded with a League-wide bonus that will give them a significant edge over their competition in Stormfall, along with additional perks for each participating League Member. These may include Skull Runes, Units, permanent modifications to their Castle or Unit statistics, or other features.
There are two kinds of bonuses for League Achievements - League Bonuses, and Individual Bonuses.
These are awarded to a League collectively upon successful completion of a League Achievement. These bonuses can take the form of ranking point boosts in the League Rankings, or League-wide bonuses to Unit or Castle statistics for all participating League Members. League Bonuses earned while being a member of one League are non-transferable, and can not be retained upon leaving that League. League Members joining a League after it has earned an Achievement will not enjoy the benefits of any existing League Bonuses. If you leave your League and join another one, you will be able to receive League Achievement bonuses only after you have been in that League for 7 days or more.
These are your personal rewards for assisting your League in completing a League Achievement – these could take the form of Skull Runes, free Units, or special items. To claim your bonus, click on the highlighted "Claim Reward" button in the "My League" section of the Embassy once your League has successfully completed an Achievement. Individual Bonuses are one-time offers and, like League Bonuses, cannot be used or earned again once you've left the League in which you received it, even if your new League earns a similar League Achievement.
To view the list of League Achievements, along with their Terms and Bonuses, go the "My League" tab in the Embassy.