kill regular skellies in said zones to make them spawn. They are on same spawn table. apperantly.
anywhos it seems to be a rare drop. From an uncommon spawn. The skellies are red and should be hard to spot when they spawn. The pain is to actually get them to spawn. And then to make them actually drop the darn thing.
Don't know whether or not they ever show up on track, but they are not "out" all the time. The sky has to go red *and* it appears to be random how many will spawn even then. I've seen the sky go red in a couple of places with lots of undead but no people killing them (Paineel's garden for example)...and the agitated skellies did not appear.