This is most likely NOT unkillable, and people sometimes know what these drop from hacking the .dat files or whatever to find out. Anyways, I'm pretty sure this would work.
You get an alliance, EVERYONE (except maybe rdms and brds..) will have /rng, including the blackmages. They will ALL have this worm on widescan, tracking it. Now you have the option of /ma Stun <scan>.
(will stun the mob you have on widescan even if its not targetted by you)
Now supposidely this thing can't run when its stunned. you just gotta have either a lot of blackmages to cycle in an out, or darkknights whatever..
The only downside is, is that before rangers were nerfed my friend did slugshot with full tp and then EES following that on this guy before he could run. He did like a good 1-2k damage (was only lvl 60 at the time) and this amount of damage didn't take the worm down a percent, least not from what he could see.
hahahaha, I see skimmers post now (sorry just looking back up at the different posts) he was the ranger >.>;
Etah ~Asura Server
http://ffxi.allakhazam.com/profile.xml?52618