Outer Realm Invasions

During an Outer Realm Invasion, you get 3 attempts each day to fight a boss and gather as many of the event currency as you can. The currency you gather can be exchanged for goodies in the Exchange Store, but will disappear when the event ends.

The boss itself will have 15 HP bars, and each bar you knock out will net you a certain amount of the event currency (as seen next to the boss' HP bar). If your team does not survive or if you cannot knock out all 15 bars in 20 turns, then you will still be allowed to keep what you gathered, but will not earn the final loot reward. Either way, you will get a choice to either keep the reward, forego the reward and try again. There is no limit to how many times you can retry if you keep refusing to accept the rewards.

The boss' strength and how much event currency it drops per bar of HP are both directly correlated with how strong your team is. To maximize event currency, you should only accept the reward if you were able to finish the boss. If you cannot finish the boss with your current team, then swap out a team member for a weaker one (or remove her altogether) until the boss is weak enough for you to finish. Each bar of HP will give less currency, but you will get more total because you knocked out more bars.

tldr; For maximum currency gain, deploy your strongest team that can still knock out all 15 bars of the boss' HP. If your current team cannot finish the boss, then refuse the reward and fight a weaker version by swapping in weaker characters until the boss' level drops (as indicated by how much event currency it drops per bar of HP).