To summon a Raid Boss, you need Entropy Crystals. Entropy crystals can be obtained by chance when performing advanced summon in the Ether Summon. To summon the raid boss, on the Map, go to the Camp and tap on Circle Raid. At the top right corner, tap "Summon".
There are different levels to summon the raid boss; 20, 40, 60, 80 and 100. The higher the level, the harder is to defeat the raid boss and cost more mp for each try. However, the higher the level, the better rewards you get. For each raid, you can participate twice. Further tries to hit the raid boss will cost you 100 jewels each. The raid boss only lasts for 6 hours, if it doesn't get defeated, it will disappear and there will be no rewards.
You can only summon one raid boss at a time.
Once you summon the raid boss, all members of the circle can hit the raid boss even if you have not attack it.
When preparing your party to fight against the Raid Boss, it's recommended that you include any Sidians that can activate the ATK multiplier: Each Sidian added to your party that can activate the ATK multiplier will add +2 to the multiplier's sum, at a maximum of total of 12. The ATK multiplier will be applied to every Sidian in your team; don't forget to include them in your Raid Party to make your team stronger!
Sidians that can activate the ATK multiplier include:
Dominant Sidians, which are dependent on the Raid Boss—each Raid Boss has up to 3 of their own unique Dominant Sidians. These Sidians are fixed to the individual Raid Boss and will never change.
Daily Buff Sidians, which change daily, but will apply ATK multiplier regardless of the Raid Boss.
All 3 Daily Buff Sidians are changed everyday at 0:00 UTC.
By defeating the raid boss, you can get materials for skill upgrade lv 4 and lv 5. By small chance, you can also obtain the raid boss. However materials for skill upgrade lv 5 can only be dropped from Raid Boss lv 60 and above.