NPCs composing that spawngroup :

an_alarm (10%)

an_explosion (10%)

an_immobilizer (10%)

an_inactive_trap (10%)

a_formless_terror (10%)

a_magi_construct (10%)

a_singularity (10%)

a_spike_trap (10%)

a_wardstone (10%)

a_wave_of_cold (10%)

NPCs spawning around that spawngroup :
(Max range : 200)

necropolis_64, range=26 (74,-2096,-255)

a_carrion_bat (100%)

necropolis_98, range=187 (227,-2027,-255)

necropolis_103, range=133 (66,-2253,-247)

necropolis_104, range=134 (25,-2249,-245)

a_Chetari_Deathbinder (50%)
a_Chetari_Dominator (50%)

necropolis_135, range=164 (37,-2282,-245)

necropolis_146, range=192 (177,-1964,-257)

a_Chetari_hunter (50%)
a_Chetari_Scavenger (50%)

necropolis_147, range=154 (211,-2168,-255)

an_inactive_trap_190092, range=152 (205,-2063,-253)