Can anybody offer a reasonable clue about how to do this? Turns out Eshwe the Insane spawns in the doggoned sulphur. Funny thing, Signets of Capture just don't seem to show up when traveling as a worm ... or am I missing something here?
I put my signet of capture in the seige attack slot. It appeared and allowed me to cap. Once I capped it, the slot changed back to seige attack.
Hope that helps.