The First Boss
Though Skeram is the first boss in the raid, he is not to be underestimated. This boss will incrementally cast True Fulfilment on a random player, charming them and increasing their damage output by 300%. Polymorphing charmed players is a great way to deal with this ability.
In addition, every time Skeram loses 1/4 of his total HP, he will cast Summon Images, creating two clones of himself with the same abilities, but with less HP. The raid should make sure to interrupt them when they start casting Arcane Explosion and focus them down. To accomplish this, you should always position three melee classes (including one tank) on each lower platform so they can focus on interrupting the images.
You should always have your tank in melee range of the boss to prevent him from hitting the player with the highest threat with Earth Shock. Finally, Skeram will Teleport to one of the two lower platforms at several points during the fight.