NPCs composing that spawngroup :

Stonegrinder_Minion (50%)

NPCs spawning around that spawngroup :
(Max range : 100)

hole_3, range=98 (424,-332,-192)

hole_10, range=64 (453,-310,-77)

hole_11, range=98 (428,-256,-99)

hole_12, range=55 (482,-256,-101)

hole_14, range=30 (492,-282,-89)

an_elemental_warrior (50%)

hole_16, range=89 (521,-210,-223)

a_citybound_spirit (50%)
a_rock_golem (50%)

hole_17, range=91 (543,-211,-231)

a_citybound_spirit (50%)
a_citybound_spirit (50%)

hole_18, range=78 (572,-243,-233)

hole_232, range=22 (495,-302,-192)

an_elemental_monstrosity (50%)
an_elemental_warrior (50%)

hole_233, range=37 (516,-262,-192)

hole_236, range=36 (487,-278,-132)

an_elemental_monstrosity (50%)

Stonesoul_the_Unmovi_189537, range=42 (478,-282,-192)

an_elemental_harvester (50%)
Stonesoul_the_Unmoving (50%)

Stonesoul_the_Unmovi_189538, range=86 (544,-217,-192)

an_elemental_harvester (50%)
Stonesoul_the_Unmoving (50%)

an_elemental_capture_189551, range=85 (461,-234,-145)

an_elemental_capturer (50%)
muck_covered_elemental (50%)

an_elemental_capture_189552, range=62 (534,-239,-192)

an_elemental_deceive_189658, range=72 (456,-259,-145)

an_elemental_deceiver (50%)

an_elemental_visier_189667, range=34 (491,-321,-141)

an_elemental_visier (50%)

an_elemental_visier_189668, range=12 (505,-303,-145)

an_elemental_visier (50%)