MegaSeadramon (Raid)uses different skills for each phase.
Time limit for killing it is 10 minutes.
This raid use 3 different skills:
Go back. You can't handle my anger. (Normal Area skill)
Player Close to MarinDevimon will be damaged.
100%~80% HP, deals 3,000 damage.
Cooldown: 27 seconds
You who betrayed the trust, be crushed piece by piece! (Small Circle skill)
The damage is divided by the amount of players in the circle.
77%~50% HP (1 circle), x4 player 4.000, x3 players 8.000, x2 players 12.000, x1 players 16.000 deals damage.
27%-1% HP (2 circles). For damage see the not at the end of article.
Cooldown: 38 seconds
Let me help you with deaths. (Normal Area skill)
Player Close to MarinDevimon will be damaged.
47%~30% HP, deals 3.200 damage
Cooldown: 27 seconds
27%~31% HP (4 circle), x1 player 7.000, x2 players 14.000, x3 players 21.000, x4 players 28.000 deals damage.
Cooldown: 34 seconds
Note: If 2 digimons on 2 circles that's 16.000, 3 digimons that's 10.666,4 digimons that's 8.000 per digimon.
Best Strategy
As soon as you start attacking Megaseadramon, just formate yourself to be one on top of the another. In other words, just stay together the whole time and don't separate.