outside Najena and Temple are a bunch of mobs. One of the rock dervish has a spawn timer of 5 minutes while the rest are around 1 min. the ph is the 5 min spawn.
I was killin dervishes in the southeast corner near Najena for a quest I got from a dark elf in PoK and had to speak to the dark elf NPC next to Najena to continue. I agree, the dervishes are the placeholder for Swirlstone. Dropped the mace but not the sleeves.
An NPC vendor offered me about 190pp for it. (I submitted the item to the database a few days ago but it hasn't shown up, so I'm mentioning it here.) I haven't checked it for item lore.
When I ran into Swirlstone I was running around killing Stone Dervishes for a task I got from an NPC near the gypsy camp, so I suspect the dervishes are PHs for Swirlstone.