Key

Keys are needed to open Boss Reward Chests during a Raid event. Each event has a key in a unique color.

They can be obtained by:
 * discovering and defeating a Hidden Boss (3 keys)
 * discovering and defeating a Secret Boss (10 keys)
 * participating in defeating a Hidden Boss or Secret Boss and dealing at least 1,000,000 damage (2 keys)
 * Daily Ranking Reward