The water will dispel your buffs, keep an eye on them
The named is harder to kill if you pull one or more bats with him.
Capture at least 4-6 (the more the merrier) of the yellow balls by carefully approaching them and clicking. Watch your health while in the water and avoid running into them since they dispell.
Use the resulting Bileburn Spores on some bats. Those bats will then ignore you if you approach, so you can pull Rallius without bats.
The bats don't "totally" ignore you. They will get aggro when you get really close to them. The effect also times out very quickly. If you're sure of your singular focus, you can nullify 4 bats and then pull him from range. The island is a good place to pull from.
After the fight, gather foul-smelling rune near ( -119, 129, -256 ) /waypoint -119, 129, -256 on his island.
"Use" it to receive a Dormant Rune of Symbiosis.
The island next to Rattigan's has a portal back to the Coliseum of Valor.
Prior to start of battle, Darwol Adan will not be aggressive, collect barrels near to where battle will occur, so that the barrels will be near-by when Darwol begins its "soul" cast. Do NOT pull Darwol on top of barrels, as it seems to eat them; The barrels just need to be near enough to click and move, Darwol roots self during "soul" cast.
Darwol Adan periodically starts spam-casting "searching for souls" and becomes immune to damage.
Pick up a barrel underwater from the pool, place it next to him, and then kill the placed barrel to interrupt his casting.
It is hard to find and grab the barrels and get back to him before he kills you. The secret is to have your pet/merc/partner attack him while you search the water and stack up barrels near to him -- but out of range of his AE that destroys them prematurely. When he starts his countdown, grab a barrel, move it close to him, then kill it immediately. Then go back to stacking barrels near him. When you have 5-8 barrels, then you can focus on burning him down, only stopping to use a barrel when needed.
Kill first the 4 arachne nest on pillars in the corners of the pool before they drop too much toxin in the center pool, raising the level. If all four nests are destroyed quickly, NO liquid will show. If it overflows, it will kill you. "You fall over, dead, as the toxic water level rises to an unbearable level!"
Nests are attackable as soon as you are ported into the room (or when you attack the named). Beware, they are often out of line of sight (or range) but don't have a lot of HP. After they are down, deal with the constant ticking damage and kill the named.
at around 50% you get an uncureable curse and the named get's damage immune. use 7 abilites (with fast cast/recast) to get make the curse go away.
Go back down the center room and kill Bahly Adan and the Manifestation of Disease.
Assure that the Grotesque Visage buff is on, as one will be able to see the conversation between Lanys_T'Vyl & Bertoxxulous on the central raised platform prior to room becoming active and the the Infected Microbes become clickable.
As soon as one gains agro from Bahly Adan, run around the room and click on each of the Infected Microbes that are N, S, E, and W of the named. You may have to click more than once after the first round.
they will turn white (instant, no casting bar). Do NOT step on the seeping shadows!
Pull Bahly Adan to the feet of the Manifestation of Disease and burn him down. Note that one can kill the Manifestation of Disease before killing Bahly Adan, which avoids the spores reproducing later. Manifestation of Disease has four increments of Microbial Cell, each one giving him 25% DR.
Kill the Primordial Malice so Bahly can't heal by draining their life.