NPCs composing that spawngroup :

an_alarm (8%)

an_immobilizer (8%)

an_inactive_trap (8%)

a_blast_of_heat (8%)

a_formless_terror (8%)

a_low_hum (8%)

a_magi_construct (8%)

a_singularity (12%)

a_tanglefoot_trap (8%)

a_wardstone (8%)

a_wave_of_cold (8%)

a_wizard_construct (8%)

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

necropolis_23, range=96 (582,209,7)

a_phase_spider (50%)
a_phase_spider (50%)

necropolis_76, range=149 (529,225,-179)

a_Paebala_warrior (100%)

necropolis_91, range=199 (477,232,-161)

necropolis_125, range=188 (611,-30,-157)

an_amorphous_mass (50%)
an_amorphous_mass (50%)

an_inactive_trap_190101, range=69 (612,102,-173)

an_inactive_trap (100%)

an_inactive_trap_190102, range=103 (626,54,-158)

an_inactive_trap_190107, range=158 (818,151,-178)