Killed him 4 more times today making the total drops over 9 kills: 5 Carpal (wrist) clay 2 Brachial (arms) clay 4 Angerspore Rings 3 Mold-Tainted Rings 3 Deathspore Cap Shields
So out of 10 kills, 5 wrist clays, 2 arm clays dropped for a total of 7 clays. Small sample size but clay drop rate seems much better than armor essence drop rate in SoD was. However, if he can in fact drop the chest piece, it must be more rare than the wrist/arms.
If you look on the map, there are 3 areas to the north, north west, north central and north east, it spawns in the north east area, and can confirm, there are 3 roamers at the top of the hill and 1 roamer that paths the water line. Seemed to spawn from any one of the 3 roamers at the top of the hill around loc 1290, -764, spawn timer to be around 12 mins on those mobs.
We just had this guy spawn on the wandering spawn. It followed the wanderers path. Within minutes of it dying, it respawned on a static sporali's spot. It did not wander from that spot. Dropped Mold ring first time, and shield second.
Also drops Angerspore ring, Deathspore cap shield, and Vitallium Encrusted Thoracic Clay. Seems to spawn off the roaming mushroom in the undead sporali area in the north.