NPCs composing that spawngroup :

an_alarm (9%)

an_immobilizer (9%)

an_inactive_trap (9%)

a_blast_of_heat (9%)

a_dark_entity (9%)

a_low_hum (9%)

a_magi_construct (9%)

a_null_field (9%)

a_spike_trap (10%)

a_wardstone (9%)

a_wizard_construct (9%)

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

necropolis_30, range=181 (440,-2068,7)

a_phase_spider (50%)
a_phase_spider (50%)

necropolis_148, range=17 (571,-2168,-256)

necropolis_149, range=149 (625,-2035,-256)

a_Chetari_guard (100%)

necropolis_150, range=178 (490,-2027,-256)

a_Chetari_Deathbinder (50%)
a_Chetari_worker (50%)

an_inactive_trap_190096, range=182 (402,-2198,-253)