Thanks for contacting World Warfare Support!
The Daily Login Eventis now available! Login in everyday to claim awesome rewards!
Login daily to receive a variety of new rewards, including City Shields, Tactic Refills, Gold and much more. Come back every day so you don't miss out on any rewards.
Additionally, the keys are used to spend less diamonds when getting a resupply pack; collect them to redeem the resupply packs when in a battlefield!
You can also check these two links out in our forums for more information about the Daily Login Event and what players are commenting about and any additional updates from the developers and support representatives: