The Slumbering Moorwalkers only appear after you have put the normal ones to sleep (they spawn in place of them, if you will). So no, they are non-aggressive, do not summon, and cannot even be attacked.
KK did this tonight for fun .. found northern moorwalker first tried clicky but said i needed to damage it a bit so i obliged took it to 60% and try again ... same message ... so then i drop to 25% and same .. only works at below 20% ... then repeated for other 3 .... same as first .. mob has to be below 20% to be put to sleep .... then hand staff to druid GL in CR ... reward is a pretty nice belt for lower levels
The quest for these bad boys is given by a druid by the northern moorwalker he says something about being trampled and the griffons makin the moorwalkers angry then gives u a wep that has a clicky to put walkers to sleep will post more when i finish the quest.
EDIT: Slumbering moorwalkers is what the other moorwalkers turn into after using the staff given by arch druid springthorn on them .
Was wandering around the NE section of the moors with my 55 Shaman and came upon an Eastern Moorwalker which conned grey. Figured I'll sic dogdog on it. What a surprise darn thing rampaged and was quadding me, had one hit for 200+ damage.
This thing was serious and took me down to half health before I "woke up", I had almost 3k hp self buffed, I tried to slow and that was mitigated. Ok I killed it but had to heal with Stoicism. I don't get that much damage from Old Wurms and Elder Wyverns in Skyfire and certainly not mobs that con grey (green) in a 20-40 zone.
I think the moonwalkers are all connected. I killed the southern moonwalker just for kicks, he dropped nothing of interest. The slumbering one popped in his place. He is targetable, but you can't attack him. I am speculating that he is linked to the other moonwalkers. Perhaps he evolves when the others are killed?
think this guys is supposed to be called Southern Moorwalker, the only time they turn into slumbering is once you get them up on the griffon's mountian and put them to sleep with quest item. they despawn after only a few seconds like this. so i think this is broken.