This is the fifth part in the six-part questchain Call of Water. Aqueous has worked out what the cause of the corruption is, and would like you to put an end to it.
I have determined where the corruption is coming from. It is the by-product of some demented research and you're going to put an end to it!
Use the pure water you obtained from Ashenvale to destroy his cache of barrels. That will be sure to bring him out.
We will have an end to this!
Have you succeeded?
It is done then! The crisis is averted and you have put in motion the restoration of the water on Bloodmyst Isle. Over time, the water, in conjunction with the other elements, will heal itself.
It is unfortunate that the blood elves cannot see that by contaminating their surroundings they're killing themselves off as well!
Tel'athion the Impure is immune to interruption from Earth Shock. He does around ~70dmg/sec for 5sec and his Fireballs and Frostbolts hit for around 120 damage each.