Extremely annoyingly, if you are at this point in the Covenant Campaign, you WILL NOT be able to kill [npc=162690] because NONE of those NPCs are there.
Yes, even before you begin the battle scenario, this will happen.
Even if you join a group and phase to their shard where [npc=162690] is up, as soon as you fly close enough it will phase you out and away, and all the NPCs (and your party) will disappear.
You probably won't be able to get close enough to tag it -- my last attempt at trying to cheese a tag before being phased out again was fly in as fast as possible on my DK, dismount pretty high up, and use [spell=207311].
As soon as I started plummeting to my demise, of course everything immediately phased away, and I was nowhere near close enough to tag it... and I just died. RIP.
So... I'd get this leg of the Necrolord Covenant Campaign done and over with ASAP, if you're farming [npc=162690].
/sigh