Guild Wars 2

I am confused about that Karka. where is it?

see #34 in the dulfy guide:
http://dulfy.net/2015/06/23/gw2-lions-arch-exterminator-achievement-guide/

When you see the distinctive pillar rock, climb above it, turn 180 and find the ledge back above the way you came up. You take the ledge all the way to the back wall and look up.

yeah, that wasn’t fun. You can hear it but finding it on your own is difficult because you botch the jump, you die and have to get another gun. Reset is like a minute.