This event has two phases: the first day is a treasure hunt. Collect chests for inner fires, energy packs, and all that good stuff. Day two is the Battle phase and lasts 5 days.
During this time you will battle Blackbloods islands of increasing levels to progress. There are 14 fortresses along this path and as a team you can work together to reach the biggest, higher scoring island. These islands will also refresh giving you the opportunity to hit the ones that give you the most points again and again through the 5 days.
Meanwhile, every 3 hours or so, a PvP island will appear just above the Skull Island that will pit you against other teams! Defeat the other team quickly for a higher number of victory points but even if your team is defeated, you can still get victory points by finishing off the team before the timer runs down so keep at it! Keep an eye on this timer in order to save a bit of energy to help your team defeat the PvP island.
As all the others, each attack costs 4 energy so ask for bigger backup on the higher islands to maximize the points you can get for your energy. But I think you will be surprised at how high you can hit these islands. Don't be afraid to try! As always, happy hunting!