Onslaught Elite location

Hi, Onslaught is the last Dervish elite I need to capture but I am not sure where it is. I have "searched" for it but found no threads and also I have looked on the xennon site but it has not been completed yet. But anyway, does anyone know where I can cap it? Thanks in advance .

there you go, gives the map for the boss as well http://gw.gamewikis.org/wiki/Onslaught_of_Terror