The puddles at the last boss just switch between 2 phases, let’s call them “active” and “inactive”:
- they are “active” during the shielded phase of the boss, when you do barely any damage to him
- they are “inactive” during the damage phase after the 3 orb clickers successfully clicked their antennas near the orbs
Once these puddles are “inactive” (i.e. doing no damage to you when standing in them) they will become these shining circles without the “vortex-like” graphics.
During the damage phase after clicking you need to stand in them to avoid the AoE damage that is happening in the whole room.
One puddle is needed right at the boss because the tank needs shielding from said AoE that is always happening in the room because once you get close enough to the boss you will get additional AoE damage from him. The 3 clickers are shielded by the clicker buff but the tank needs to tank this damage completely, so the other AoE in the room should be avoided by standing in a inactive puddle near the boss.
Kiting there works pretty much the same as it does at the other bosses -> the person furthest away from the boss places the puddle.
- tank with healers stands on one side, they HUG the boss, they move so close to him, that his hitbox starts to block them from going any more forward
- kiter stands on the opposite side, the kiter takes some steps back so he is the one that is standing at a little distance but not too far away
- after rapture you stand somewhere in the room where you like and place another puddle
- after the damage phase ends you run in again and repeat everything
The reason why the puddle at the boss is not allowed to be too far away is because the tank needs to be in melee range to the boss, otherwise the boss will use Smite and hit the tank for ~6k damage.
Here are some of my incredible unmatched paint skills to visualize it (I know, looks a little messy but I did it in ~5 minutes…):
After Rapture and clicking:
After the damage phase ended you repeat from the first picture again.
That’s basically everything you need to know about the fight.
EDIT: I forgot about the bomb, Evito explained it in his post.